Thanks so much for putting this out there. I love it. Instead of plywood, I had some pallets that had boards on top that were 10.5" wide Was able to use a few of those and built 5 of these. Instead of the extra pieces that you put inside, I instead cut a 1/4" dado on the inside before I assembled the boxes. What this means is that it is exactly the same size inside and out as a standard deep. I'll be affixing basically an inner cover that is flush on one side on the bottom. My goal was to see if I could build your setup with a standard deep box and just modify it a little. That way, anyone should be able to order a deep box and cut some rabbets and some holes in it. I also made the frame rests the 13/16" like you have in your plans. It should have minimal effect on a normal frame. I always seem to run out of deep hive bodies. This way, I can have some spares if I need them.
Here's the other plus. I plan to take out 2 of the sides and just leave the center divider in for the winter - meaning, I can try to overwinter 2 hives that share the same deep box. I'm trying to figure out the best way to stack them too. That could get a little tricky. May still need to put 2 5 frame nucs on top to super them. Probably just better to make more solid nucs, or order them.
Anyway, thanks for the plans!