I just found a nearly mint RB Series B 3x4 and I'd really like to shoot 3.25"x4.25" fuji instant film. Anyone had any luck with a back that would fit onto one of these without irreversable mods?

yesterday afternoon i modded a Polaroid 405 back to fit my 3¼x4¼ Super D with Graflex back.

to my delight, it works like a charm--no light leaks or modifications to the camera itself.

i like being able to carry around the smaller 3¼x4¼ camera while shooting Fuji instant film packs instead of a 4x5. one caveat, however, is that the rotating back cannot rotate with the film holder in place due to clearance. it has to be removed first and replaced after the back has been rotated.

What did you do to modify the polaroid back?

created a 'chimera' of sorts using an old Graflex film pack back.

along with some drilling, grinding, sawing and creative lightproofing...

ITS ALIVE!!!