Here are some recent pics of the sleeping platform I built. I read through about 20 build threads and took my favorite elements from each. I didn't want to build a platform that was permanent and render my truck bed useless for Home Depot duty, so I built it to be flexible.
The main thing I learned about this was that the measuring tape will lie. The bedliner shifts around slightly, so I built this thing by trial and error 'till it fit.
Started with this:
Then made some plans:
with a temporary top to get me through girls' camp for a weekend.
and this is how it sits right now. Not quite done, but definitely usable.