I love shooting Polaroids with my Mamiya Universal, and that's what I primarily use it for. However, I have always been frustrated at the minimum focusing distance for this camera. If it only went a foot or two closer, it would be enormously more useful to me. It occurred to me that a sensible solution might be to add the smallest extension tube. However, it seems like this only works with a ground glass back - quite incompatible with the handheld photos that I'm hoping to take with this configuration. I recently purchased a spare Mamiya Universal camera body, and I'm wondering if I could just recalibrate the rangefinder with the extension tube installed, leave the tube permanently on the spare body, and just switch to that camera body whenever I wanted to take closer pictures. This led to a few questions - I'm hoping that some of you who are more experienced with the Mamiya Press line may have answers or suggestions: a) Is such an adjustment even possible within the adjustment limits of the rangefinder mechanism? b) Would the same adjustment work for all of my lenses? c) What's the difference between the extension tubes (between lens and body) and the extension boxes (between back and body) and is there one that would be preferable for this procedure? Do I have to use both? Thanks so much in advance!