This is an interesting question!

Even with sheet film, bending the plane is tough. I tried it. In the end, I said to hell with it, as an f250 gives really close to a 90 degree view, and a little distortion on the edges is okay. It's pinhole.

Never had an issue with vignetting.

4X5 I think is the way to go. If you are making your own cameras, may I suggest those 50 cal. ammo cans, as they are impermeable to air, water and light. You can drop them from heights. They can fall off the side of the boat, no problem. They won't let you bring them on an airplane, though.