PP: I have also little challenges to make base clamps smooth and same time hold tight. I have found out that the the adjustment has to be made very carefully. Not too loose but not too tight. The window is rather small. Also you need to regularily re-check the bolt/tightness. Also be absolutely sure when you close your clamp that it is straight up. I mean that when you tighten the base clamp the string should not be twisted at all. If your base clamps are too tight it will be difficult to have base clamp moving loosely enough in place prior tightening. I also have found handy to hold the base clamp with my hand while tightening/lockin it. Third thing to look into is cleaning the rails with alcohol often enough. I would not lube them so cleaniness is vital for easy clamp movement. I hope this helps.