YES. If someone could figure out how to do this with 5x7 I would bow down to them in WORSHIP if they put plans up. I'm pretty handy with a number of fun tools.
I think what will end up working best is a system somewhat like the Mod54 setup. I mean, it's pretty neat. It would be pretty easy to homebrew, really, and I think you could do 3 5x7 in the same Paterson tank that you can do 5 4x5 in. I'm going to hit Lowes this weekend because, well, I like it there, so I'll see what I can do. I'll burn a sheet of 5x7 for the cause. I found a film holder hiding in my daughter's room that's loaded.