Bending Masonite Backdrops Revisited

I've been collecting a long time and am now working on my first layout with my grandson. It is a two foot shelf (wider in some spots) that goes around the room. Most of the track work is finished and it is made to be mechanically and electrically broken down into four shelf sections, four leg sections, and an angled bridge section to get past the door (I cry when I hear about guys that finish a nice layout and then break it up when they move, or for other reasons) so that, hopefully, someone might take it after I croke. The three corner disconnect points are 45 degree angles into the corners with floating

6 inch rail sections to cross perpendicular to the seams. I painted the entire room sky blue but now think we need to put in backdrops. Any ideas on how to put in curved masonite backdrops into the corners and make them detachable? Should they span both sections or meet in the middle? And how high should they be? Thank you.