Re: 20 MOA base Help!!
If your rifle has base spacing the same as US commerical rifles, then you should be able to get a Farrel base from companies like Midway, and Graff. If not, consider a set of Burris Sig rings with inserts. The inserts will be able to give you up 30 MOA of tilt/elevation which will be enough to solve your problem.
Personally, I would go with the Burris rings since it is a no brainer and well priced.