film flatness is only a problem with 120 (or 220) if you use the lens wide open and have a bend in film path before the frame Some TLRs are ok but lots of pro cameras are not but in normal studio use motor drive and several assistants reloading backs eliminated problems

film flatness with 35 mm with the Barnack reverse wind can make tank loading with plastic spirals difficult

the aprocapral story is the two Christmas trees and one bikini film