Hey there! I'm raising my first flock, so I can't answer all of your questions, but can a few. -- If you have two roosts, you should have them side by side, with enough room for chicken butts between each roost, so everyone has enough room if they are choosing to split up and sleep on separate roosts. You can put one above another to save some room, BUT there are some things to consider --
a.) All the birds will want the highest roost, as Chickens seek the highest point available to roost. Makes them feel the safest. As the pecking order starts to be established, fights will likely ensue, or - they will all decide to sleep on the top one only, and you will have wasted your time and $ putting in 2 roosts. If you're gonna have a very large flock and you need 2 roosts, I'd recommend putting them side by side at even level with each other so one is not more desirable than the other. They still may tussle about who gets to sleep next to whom (according to pecking order), but I've heard that those little squabbles are much more tame than the fights over the highest roost are.
b.) If you put one roost directly above another, like ladder rungs, the top birds will poop all over the lower birds all night. Nooooo fun. I have seen that most chicken farmers who choose to do an over/under set up, will stagger them diagonally (like stairs) so that the poopers on the top don't make poopees out of the lower girls.
I have a flock of 7 - all different heavy breeds. I have one 8ft long roost. There is plenty of room for all the ladies with room to grow (they are 13wks old now and fairly large, but they still have some growing to do). They take up about 3 ft of it now, as they all love to snuggle so close to each other that I wonder how they don't get too hot at night. There's room for any of the girls, if she gets temporarily shunned by the others (as can happen in flocks from time to time) - to be able to sleep off by herself (but still on the roost so she can keep her dignity) without the others hassling her & making her sleep on the floor.
My poop board is too shallow. It is an 8' x 21" metal garage door section (for easy cleaning). The roost is situated right in the center over it (so the girls have fluffy butt room between them and the wall of the coop), so there's not much room on either side of the board for them to jump up onto the roost. I tried to tell my husband it wouldn't be deep enough for heavy breeds to comfortably and safely jump up onto the roost or off the roost from, but alas....husbands don't always like to listen. LOL -- I have watched the girls navigate the thing for a week now and this is what I've found-- My heaviest girls - Buff Orpington, Delaware and Barred Rock - make it work pretty well, but they clearly aren't comfortable with it, and sometimes slip off to the floor in the process. Part of that is the slippery bedding on top of metal, but part of it is that it's just too narrow. As they get heavier, this COULD lead to broken toes or legs, even though I have deep litter for them to land on. I am most concerned with the fact that since it's not comfortable for them to jump down first to the board, then to the floor of the coop - they tend to kamikaze off the roost to the floor. Yikes. Luckily, the coop is large enough inside, that they can get some flaps in to land a little softer. I will be remedying the situation with a wide board, laid flat and flush to the end of mine to add room. I think it will be just what they need. All that to say; Your wee little bantams would have an easier time of it, than my jumbo clucks I'm sure, but I think I'd still make that board deeper than my 21 inches if I were you. Obviously, if you're going to do two roosts, that poop board is probably gonna need to be doubled I would imagine?
My board is about 14" off the floor. The girls haven't needed a ramp at all.
I hope others chime in to help answer all of your questions! Congrats on your fluffy babies! Enjoy!
