The Tikka base and rings should be the Optilock system being a stock set and if so, I don’t think you can move the base forward at all. I have a set on my Sako with the same system. Both rifles have the integral dovetail rails and the bases have to be tapped into place to be nice and tight to fit the tapered rail. On a side note, the lowest set of Optilock rings can accommodate up to a 56 mm obj. lens so I really don’t see you having a problem. Good luck...