Well that supports the saying "necessity is the mother of invention", looks good. By the looks of your pictures (background) you don't paint the edges? I'll bet you could with a stand like that. I managed to come up with a completely different approach, and I don't stack them because I like to paint the edges too. I hang the box off of a 2-by, I can paint a side and two edges, flip it 1/4 turn and paint again. Repeating until all 4 sides and 8 edges are done. I pull it off and find a place to hang the box up until dry, always handling and hanging it by the inside. Alternatively, if just doing a few one could rest a 2-by on two sawhorses with the 2-by running through a few boxes. Paint the boxes, rotating them until done and just let them hang between the sawhorses until dry.