The Shen-Hao HZX will take a 90 on a flat board and can focus it to infinity with just the standard bellows, although you'll basically have no movements because the bellows are extremely compressed. Add in the bag bellows (a $100 accessory, and well worth it) and you can use a 75mm on a flat board. You might well be able to use shorter lenses than that, but I don't know as I never had anything wider than 75mm.