Brian, one thing you are overlooking... The lens barrel itself may show 7'... It might be slightly off either way. Secondly, each body could reflect different readings because the little lever that engages the lens could be off also..... While I understand you want to be abe to interchange the lenses. That is something that might be more trouble than it's worth. In an ideal world, they 'should' be the same, but in reality, with tolerance differences, that will NOT be the case. An easy compromise would be to split the difference somewhere in between each and stop down. As others have said, try using a ground glass screen with the back open to truly check focus. It could be that the rangefinders on both are accurate, but the lens barrel does not reflect that and that's something that might not be adjustable.