Obviously I meant 5x4 above, but then I think you realised I'd made a typo.
I'd never really thought about making it 5x7, but that does indeed make sense. I could either do basic carpentry (using a lathe and milling machine is more my thing) or "contract out" the woodwork to a friend who is a demon cabinet maker. I've got no idea how much a bellows will cost, but hey, its only money... must get back to ebay to scout for lenses. No lens, no project... I've not yet checked out film availability and prices, and I've not currently got developing kit, but I used to do 35mm and 120 in reasonably large amounts for a casual amateur, so that won't worry me.