Eddie, the columns look terrific! /forums/images/graemlins/cool.gif
I had to look long and hard to even come up with a suggestion, but I'm not sure about your footing around the base of the column. Did you leave a ledge to support the rock veneer? If not, you could probably still pour a base footing around the column up to the level of the rock. That will ensure there is always support and also reduce the likelyhood of things constantly bumping into the stone at the base.