I got it pretty close to straight. I'm not going to chase this panel to perfection - it's just going to get dinged up as -I- use the truck.
First, some brainstorming, because people don't seem to have a lot of detail in their builds to follow. That, and maybe I'm a little fussy:
I sliced the 2x4x0.063" rectangular tubing to an "L" that is 1-1/4"x4", and welded some flats on the ends so I can plug weld them to the bed. This is a LONG stretch to weld, and it's going to warp all the heck, so plug welds are a good idea.
I will place a length of 1x2" to create a new "back" to this, to recreate the raised stop at deck height. Should all look like this:
Then I cleaned and scrubbed all the skid strips, angle strips, and blasted bits and epoxy primer. I'll give that a few days, and then weld the front and back back on.