Spent more time figuring out the reinforcement box and settled on simple. The nutplates that will be attached to the backplate will be riveted through the wing skin, through the reinforcement frame, and through the L-Channels. I figure this will give the strongest support. I may have to wait until I get back from Oshkosh (just a couple of weeks) for buying a deeper squeezer head. Anyhow, today I cut out the rear frame using 0.025, then cut some L-Channel to fit. On the front of the L-Channel I shaped it so that it will properly fit over the main spar angle (on the bottom). I also pilot drilled the horizontal holes on the OB side L-channel brace so that once I lay it down on the wing skin, I can drill-in-place and rivet to the IB side of rib #7.
Also had to dissassemble my air shears twice because it kept siezing up....grrrrrr