I'm struggling a bit now to rough out designs for the framing for the bed extension. The shell was all big, rough, measurements, but everything here is in fractions of an inch and there aren't any direct ways to measure relationships between points without disassembling. I might just need to pick up some metal and assemble/measure as I build it on the truck.
The extension frame (most of the green lines below) will attach at the rear bumper mounting points on the frame and to the bolts on the bed that hold the tailgate upper latch in place. The bumper will extend out past the end of the tailgate. I'll put some kind of x-bracing to make the extension rigid. It seems like I get rear-ended about once every 2 or three years, so it'll be good to have the bumper sticking out there.
I might notch the bumper mounts somewhere so that if I am hit, it bends downward, deflecting energy away from the shell. If bits of metal that extend the bed are kept lightweight, they'll distort down with the bumper w/o tweaking the bed.
