Thanks for the interior door tip!
We plan to use Lorna's interior door idea to create our walls. I had to search back and find the thread where I first learned it. The area restore has interior doors that I hope to pick up and repaint if they are there when I return from a trip in a about two weeks. I'll trace the curve I cut from the shower stall. One will go on each side of the shower and one on each side of the bath area across from it which will hold the toilet and sink. These are right in front of the rear wheel wells so another will be used on each side to create the storage above the wheel wells. Quick, easy, sturdy, premade, cheap, and square where it counts. Screws from below the floor will hold the bottom of each in place.