The doors are an interesting idea, given that much of my frame is 24" wide. I'd need a 96" door, a 75" door and a 90" door. Can they be cut down without compromising their strength? 80" and 96" are common heights. I don't think anyone makes a 75" door...
I'd also need to figure out how to support the wider area shown in the lower-right and upper-left portions of the drawing.
George
George, I built my layout on a door with 2 inch foam. It was very easy to do and very strong. The doors are already square and you can lean on them. The only issue I had was dropping the feeders was a little tricky. I ended up using a plastic straw as a feeder tube. I used plastic heavy duty shelving from Home Depot for support and storage under the layout.