Been studying Anti-Cant Devices - lots of searches and reading here. We've pretty well hashed out why they are useful, but there is an aspect that I don't see covered very well - do you find it best to have it mounted on the base/rail or attached to the scope? It seems to me that base could be a little off from the crosshairs. What I'm talking about is that because of tolerances in the receiver, the bases themselves, the rings, etc, it would be reasonable that if the scope hairs were vertical, the rifle might have to be off vertical. This might then make the base off horizontal and therefore the level would be off. Does this matter? do you guys have a preference? Why? Thanks!