Our travel trailer had the head of the bed in the slide, and a box to support the rest of the mattress. It ran across the width of the trailer. We have removed the bed completely and the box and plan to put a mattress & boxspring set on a metal frame, just like in a house. It will now run with the length of the trailer. The headboard will be the bottom part of the wall on that end of the trailer, and he is planning to build pieces to accept the 2 legs closest to the wall, so the bed won't move when we are using it.
Hubby plans to use a tie down strap, hooked to eye bolts on either side of the slide to simply flip the bed on its side and strap it in for transit. He is custom building drawer storage in the slide, so the bed will keep the drawers closed during transit, as well.
We hope this will work, the numbers seem to support the idea, but we are not quite there in our reno project yet. This should give us more floor area for transit storage of the large outdoor trashcan we use to store our outside carpet in, as well as our folding chairs which used to live in the bed box.
Here is my website, which chronicles our project:
Traveling Teacher. I will be updating the site as we progress toward the end of our project.