The 197mm is actually 197mm square. You got me excited there for a second--I am planning to modify a B&J and build a 5x7 back for a Kodak Master View 8x10, so I looked at the 4x5 again--much lighter if it would work. However, the way the bellows mounts through the back of the Wisner and is held in by the film pack/focus panel, the bellows back limits the exposure field to about 6 inches in each direction so that the back can be rotated 90 degrees. I can manage that much wood working, but not much more.