Looks great so far! Nice job! I am a little weary on the roost for them though. It is often recommended not to have any kind of roost in a pen/tractor/coop for meat birds, such as CornishX's. If they are able to get up, the can get very badly hurt trying to jump down. Obviously your roost isn't very high up, which helps, but I would be concerned it could still cause problems. Perhaps someone with a lot more experience could chime in on that one...
I am so thrilled you showed the pictures with the hinges... I know it sounds silly, but when we built our pen, no matter what DH did, the hinge part ended up with a 1/4" gap and lets the rain in. Thus we have this awesome tractor/pen...but its covered with a tarp. Seeing the pictures of how you hinged it (in the middle..so both pieces flip up... )VERY HELPFUL!!! Thank you for sharing.
-Jessa