Hope someone who uses one can help. I just picked up a RB67 Pro-SD 645 back for 220 rolls for a project from KEH. The back looks very new and everything appears to work well. However, I discovered that it will only do 30 645 frames on a 220 roll. The frame counter reached 30 and the roll also reached the end. I found the frames are spaced at nearly 15mm apart. Is this right at all? It looks like the counter won't continue above 30 this seems to be what is designed in the back. But then why? Why frame spacing is so wide? Isn't it supposed to be 32 frames on a 220 film for 645 format? Does this mean frame spacing for this back is bad and need repair? Wasting 2 frames is not really a big deal but such a wide frame spacing looks really stupid. My Pentax 67ii has a 3-5mm frame spacing and yields 21 frames on a 220 roll. It would be funny to switch to 645 from 6x7 only to get 9 more frames out of a roll of 220. Can anyone answer this question please. Thanks a lot.