Why settle for might be good. Just get the 30 moa base. It’s not that much more expensive and any scope that has enough adjustments to zero with a 20 will allow you to zero with a 30. You get the extra 30 moa (or about 8.5 mils).
Most scopes depending on how it zero’d out will give you about half of what the labeled adjustment is. So if you have a 34mm scope with 30 mils total adjustment…that will put you about where you’ll be at 1760y which is about 15 mils plus or minus. Or about 55 moa. Looking at some of my old dope from years past.
I haven't shot my 338 Norma to a mile but the ballistics on my load indicate about 60 MOA, for my weather and elevation. Most guns have a little variation in zero as well. You might loose a few MOA from the get go. With the right combination of scope and a 20 MOA rail, it can work. A 30 gives more room for error and potentially more scope options.
You could always hold over if your scope has a graduated reticle.