The shelves are a great touch and look nice. I'd sure like some more information about how you built them. When you use the aluminum tubing, how do you join it? How did you make the pattern for the shelf top? What kind of material did you use?
The aluminum tubing is, of course, riveted together. I did use larger (3/16") rivets most places. It is very sturdy.
The shelf was simply made by building the rectangular bed frame and pushing it as far back as it would go. It leaves curved spaces in the rear and on each side. I then used plywood to make the two sides and used 2x4 on the inside to secure it to the floor. I secured it directly to the new bed frame. I attached some aluminum angle to the side wall for a support bracket and then droped a piece of plywood in the top. Some small pieces of 2x4 on the inside of the side wall 3/4" down from the top made the shelf on the bed side so the top could sit right in flush with the side. Then just screw in to the alluminum on the exterior side and the 2x4 on the interier side and cover it with whatever you want.
The rear is done basically the same except the back wall comes up from the top of the bed frame behind where it hinges. The top is secured the same way as the sides. Once you have the aluminum bed frame constructed and in place, the construction of the side walls and shelves pretty much gets dictated by the space that's left. Be sure to leave a little room to tuck in comforter, etc. Also, I covered the side wall with pleather with some polyester filler so I also needed to leave room for the padding as well. I am completely satisfied with the way it turned out.
The patern for the top pieces was made with butcher paper. Very simple once the sides are built up.
Also, did you lose the under (twin) bed storage access from the exterior on the one side? What did yo do about that?
The storage is only accessible by liftiung the top. I considered trying to incorporate the original storage bins (as the PO had) but it would never have been right. I also could have easily made the front to open, but I opted for the single large storage space accessible through the top rather than trying to keep the front access (there is NO access to the sides as the bed and shelves span the complete width of the trailer).