Dustboy, I started out similar to you - a Leer topper w/ a storage platform / bed inside. I thought about using an ARE vertical side topper, then thought about a flatbed w/ a vertical side topper on top.
I finally went w/ a Callen camper custom build. I love it. It has a cabover for easy to access storage when the benches are made into one big bed for my girls and myself. Anyway, the build link & pics are
here.
I can take the benches/ sleeping platform out in 5 minutes. The rack on top allows for canoes, lumber etc. Here's one pic (click on the pic for a larger view):
Callen uses aluminum skin over a steel frame. I'm not sure what material screws are used.
I'm going to have a rear bumper made w/ a 1/2 width fold down tail gate/ storage system. That way I can open one back door without dropping the "tailgate".
I need to update my build thread. I have an awning & a water system now. Webasto air heater (diesel) to be installed real soon now.
Hope this helps - steve