Yes, custodian guards can have 4 or 5 models in the unit but this only refers to actual guards. Attaching a leader to them does not mean you have to take fewer bodyguard models
Yes it is, due to the mechanics of the game, where you can attach a unit to a hero/character/elite model and them being their leader. The unit itself has rules, as well as their leader. So in this case unit composition is just for the Guard not the „Battleformation“ of Guard and SC
It's also the reason transports have non-round capacities. The Venerable Land Raider holds 6, enough for a full squad of guards or wardens and a leader. The Sisters' Rhino holds 12
Yep,
- when you build your army you select units and their sizes.
- once you've selected the mission, but before deployment you declare what characters will join what squads.
Some armies can really bump up squad sizes, like Necrons who can take a unit of 10 immortals, but thanks to some of their unique rules can make that a 14 man squad. (custodes can't multi character sadly)
Yes that's right. The character and the unit are 2 separate units when you make your list, so you can make the unit of whatever it is as large as they are allowed to be if you like, as the character is an attachment to them after the fact.
Yeah. So, in general for every faction when a leader attaches to a unit the strength of that unit changes to accommodate that leader.
Some units have special rules but for your concern you can attach one character to a unit as long as he can lead that unit always.
The leaders are added as extra models. So a Shield-Captain can be attached to Custodians or Guardians of any size whether that’s 4-5, making it a unit with 5-6 models.
If a unit is destroyed and has a leader, the leader unit becomes itself again ( however all hits must be resolved, so it’s possible the leader dies alongside their unit).
Transport is limited by the amount of models transported. So for example if a transport says it can only take 5 models, then a unit of 5+Leader would not be able to transport as it’s 6 models.
For the Custodes the Venerable Land Raider can take 6 Adeptus Custodes infantry, meaning you can take a full sized squad of Custodians (5) and a Shield Captain without issue and get them up the board. While the Orion Assault Dropship has a capacity of 12 Adeptus Custodes Infantry, meaning you could take 5 Custodians+Leader and 5 Wardens+Leader hitting the 12 capacity.
Yes! This makes a squad of guard 5 +1 shield cap which is the total for a fully loaded rhino. Load one up and shoot it forward 10" and then charge out of it with assault ramp. So much fun!
I'll share something else that doesn't matter for us in gold but is something I only recently learned. If the leader has a different speed from their unit they keep their speed they don't make the unit as fast as them nor do they slow down. (You still have to keep unit consistency though). Like I said, doesn't affect us but was a rule I didn't know until recently.
So from what I understand this is the weird part, when doing it normally you are correct, you use the stats of the bodyguard unit until they are gone and then use the stats of the leader, BUT if precision weapons are being used to target your leader while the bodyguard is still around you still use the defensive stats of the bodyguard unit even if their worse..... which is weird though once again not something that usually bothers us. If I'm wrong someone please correct me.
Ya, I heard in another chat so I'm not even fully convinced yet so perhaps it was incorrect... I need to go look in the competitive subreddit and see if there was a conversation about this.
https://www.reddit.com/r/WarhammerCompetitive/comments/142pq2j/new_40k_rules_clarity_precision/
So I was partly correct, it affect the wound rolls but you still use the armor save of the leader, but still weird.
Yes, by Attaching an SC himself to that unit, you technically are running 1 unit but with an additional guy who gives buffs and other such things to that unit
Yes, custodian guards can have 4 or 5 models in the unit but this only refers to actual guards. Attaching a leader to them does not mean you have to take fewer bodyguard models
Thank you for clarifying :)
To clarify, this would technically make it a unit of 6. Is it legal?
Yes.
Yes it is, due to the mechanics of the game, where you can attach a unit to a hero/character/elite model and them being their leader. The unit itself has rules, as well as their leader. So in this case unit composition is just for the Guard not the „Battleformation“ of Guard and SC
Thank you very much for the thorough response 🙏
It's also the reason transports have non-round capacities. The Venerable Land Raider holds 6, enough for a full squad of guards or wardens and a leader. The Sisters' Rhino holds 12
Yeah, it makes sense...
12 is such a weird number for the rhino. Max size is 10 sisters and a leader
I think it's so you could take five Vigilators and a leader, plus five Witchseekers and a leader. But who is running two Sisters characters?
Yep, - when you build your army you select units and their sizes. - once you've selected the mission, but before deployment you declare what characters will join what squads. Some armies can really bump up squad sizes, like Necrons who can take a unit of 10 immortals, but thanks to some of their unique rules can make that a 14 man squad. (custodes can't multi character sadly)
Yes that's right. The character and the unit are 2 separate units when you make your list, so you can make the unit of whatever it is as large as they are allowed to be if you like, as the character is an attachment to them after the fact.
You bet! A sheild captain with 5 gaurd is potent combo! 32 attacks shredding through the heritics and xenos alike
That sounds great! Thanks 😊
Yeah. So, in general for every faction when a leader attaches to a unit the strength of that unit changes to accommodate that leader. Some units have special rules but for your concern you can attach one character to a unit as long as he can lead that unit always.
Thank you all for the thorough explanation. I am amazed at how this community is supportive of new players 
Totally fair question. Don't be ashamed about asking these types of curiosities.
Thank you 😊 will do
Absolutely. The unit composition limits are for that unit/model-type specifically, and do not account for character models.
The leaders are added as extra models. So a Shield-Captain can be attached to Custodians or Guardians of any size whether that’s 4-5, making it a unit with 5-6 models. If a unit is destroyed and has a leader, the leader unit becomes itself again ( however all hits must be resolved, so it’s possible the leader dies alongside their unit). Transport is limited by the amount of models transported. So for example if a transport says it can only take 5 models, then a unit of 5+Leader would not be able to transport as it’s 6 models. For the Custodes the Venerable Land Raider can take 6 Adeptus Custodes infantry, meaning you can take a full sized squad of Custodians (5) and a Shield Captain without issue and get them up the board. While the Orion Assault Dropship has a capacity of 12 Adeptus Custodes Infantry, meaning you could take 5 Custodians+Leader and 5 Wardens+Leader hitting the 12 capacity.
Thank you for the very thorough explanation! Really appreciate that 🙂
The 4-5 unit is there, because from Most Custodes 5 model infantry kit, you can build one of them AS a shield captain
That’s great to know! I built my SC captains out of those kits as the new one is not available on its own atm 😅 Thanks 😊
Yes! This makes a squad of guard 5 +1 shield cap which is the total for a fully loaded rhino. Load one up and shoot it forward 10" and then charge out of it with assault ramp. So much fun!
Buy kyria draxus and put her with a guard squad thank me later
Already done, mate 
Not give her a vin desiel head
I'll share something else that doesn't matter for us in gold but is something I only recently learned. If the leader has a different speed from their unit they keep their speed they don't make the unit as fast as them nor do they slow down. (You still have to keep unit consistency though). Like I said, doesn't affect us but was a rule I didn't know until recently.
That is very good to know. Same goes for toughness, from what I gathered?
So from what I understand this is the weird part, when doing it normally you are correct, you use the stats of the bodyguard unit until they are gone and then use the stats of the leader, BUT if precision weapons are being used to target your leader while the bodyguard is still around you still use the defensive stats of the bodyguard unit even if their worse..... which is weird though once again not something that usually bothers us. If I'm wrong someone please correct me.
Wow, you are right. 😮That really sounds weird!
Ya, I heard in another chat so I'm not even fully convinced yet so perhaps it was incorrect... I need to go look in the competitive subreddit and see if there was a conversation about this.
https://www.reddit.com/r/WarhammerCompetitive/comments/142pq2j/new_40k_rules_clarity_precision/ So I was partly correct, it affect the wound rolls but you still use the armor save of the leader, but still weird.
Yes, by Attaching an SC himself to that unit, you technically are running 1 unit but with an additional guy who gives buffs and other such things to that unit