Hi I don't post much, just read thing, but I have a pretty long history working with guinea's so I thought I would chime in.
Your correct about the perching, but don't build a perch that is multi level, that tends to lead competition and the roosters will definitely start fighting for pecking order over something that simple next spring. The hens not so much but they will instigate the fight to pick a mate and multi teared perched just makes it worse. 2x4's work good for perches. Lean two type structures are really good for a coop but whatever you build make sure they can see outside equally. Think it through and look for competition choke points.
You didn't say how big the trailer was but as they grow older they will want to spread out into there little clicks. Not giving them that room can instigate fights amongst the hens. And they tend to really be the problem. They want to live in
trees at night and eventually they will find a good clump of cover and start laying eggs. The rest of the flock will begin to ignore them at that point and if your in a "Wild" zone with predators they'll start disappearing. When they start hitting the trees at night and they will, that is when the pecking order will ensue in the roosters and fights start to break out over who is king. Trees are multi level perches.
The best practice is to start them at a young age by opening the cage door, letting them slowly creep out then come up with a signature call "Hungary Birdies" and clap a bit and coax them back in. Do this daily, so they get that they are supposed to go in. Re enforce as they grow older by doing that before feeding. It doesn't take them long as juveniles to get the picture. This will help some.
Next year when they start trying to take to trees. Make that a bad decision but stay very calm when you do it. Throw pine cones or small object in there direction. As they come to ground use the signature call and clapping to drive them back to the cage. Hopefully you get all them down and back in then keep them locked down a day or 2. Eventually this may not work anymore as they grow older and dumber then rest assured if you have any night predators, Owls especially, they will do the convincing at that point that it is not safe outside at night. Accept the loss and hopefully they decide to go in after that. Well accept for the nesting hens.
With 20 birds your going to have your hands full. They are going to travel. Expect t0 see them at your neighbors house even if its a couple miles away. LOL
One thing a was very big turning point in a guineas behavior was switching them or raising them on organic food. Guinea behavior is dramatically different when fed anything that contains GMO. I used to
feed Purina Game Bird and the Fowl would just go crazy and do everything they could to get themselves killed. They would get to a point that I could not do anything without causing them stress, which would lead to bad behavior. Now I feed them a 100 percent organic Broiler food and their disposition is very calm and very trusting. They look forward to that nightly feed and rarely do anything that is not within a predictable nature. They are also real friendly, often hanging around us and the dogs real close just to be with us. It was so different when we were feeding GMO Purina. Just drama 24/7 with them.
Last advice I can give though is do not fall in love. They die a lot. Everything kills them. I had one die who choked on a
mouse it tried to eat. They do a good job with bugs and they are worth renewing the flock if needed. They are also very good at being watch dogs for everything that doesn't belong.
Matt
Came back an Added this..... You want about 8 square feet per bird if possible. That tends to lead to lowest amount of stress. But then there is financial reality too. Just give them as much space as you can afford too.