Nothing wrong with using a 20 MOA base even if you don't need it often. Yes, theoretically, you will have approximately 40.5 + 20 = 60.5 total up. Scope-wise, the SS is one of the best starter scopes, the 3-9 will be good for hunting, but will make 1-2 MOA targets at distance a challenge. A fixed 16x SS would be better for matches, but then no good for hunting.....