I am just trying out my Hv20 with Brevis 35mm adapter + Flip, and the problem is not centering left to right, that's easy, the problem is that I lose at least 25-30% off the top when I zoom in! There is just not enough play in the system to compensate for that amount of loss. I must be doing something wrong because no amount modifying the set screws will change this. Otherwise everything is sharp corner to corner. Any suggestions?