here are a few sketches i made showing the dimensions i used.
these are my hinges. Not sure if they differ from the JK ones.
-I began by laying a 12mm ply floor, covering the whole cargo area. The bed is 18mm ply
-I made these side bits pretty much by looking at pictures off theSamba and using some guess work.
-the front/heel board is 17" high and 60" wide.
-The 2 side panels are mounded to the front board via a 1x2" batton.
This gap has since been covered up
-A 3rd batton is fixed to the rear bulkhead. Level with the front board. This allows the back to rest firmly in the bed position.
-My back board is 13" deep. The base is 20" deep. (this took me a while to figure out :x )
-by putting the hinges in the bed position, i mounted the boards to the hinges first.
-then i mounted the hinges to the side panels. Job done!
-Because mine was a fill width i needed to screw another batton under the seat base to stop it flexing.
Its now rock solid, and i think the dimensions work well. All you need is a day, some sheets of ply and basic woodworking tools. Hope this helps.