Let me see if I can answer the questions by explaining how I made the shelves. I took some pic just in case someone asked. First I started out with PVC Garage Door jamb moulding from Lowes - Item number 98009.
http://www.lowes.com/pd_98009-1487-0...3342086&rpp=32
A 7' long piece cost $12.99 here in Florida.
The back of the jamb material is ribbed so it was easy to remove all but one rib to make the piece "L" shaped ( I used a stacked dado on my radial saw) so it would overhang the front and stay somewhat straight. See pics. I then measured the distance between the bathroom walls and the outside shell - in my case it is 3 9/16. i ripped my piece to that dimention. I cut it long enough so it would be held in place by installing it behind the walls. (around 60") The wall between the bath and kitchen moves so I put a small piece of Velcro to keep it from moving. The shelf installs in seconds and must be removed to close the Trailmanor. The right side of the shelf had to be notched around trim - see pics.
The kitchen shelf is on the wall top on the left and covers the vinyl flap on the right. The flap already has velcrow there so I put the opposite piece on the bottom of the shelf to hold in place. It's a little wobbly because it sits on the flap until you place something on the right side - then it's rock solid. Both sids of the Kitchen shelf had to be notched around things in the way. It is also held on the left side by putting it behind the wall. I used the same technique ( removing ribs) to make the kitchen shelf.
Hope I covered everything,
Ed