Re: Basics of ring bases
First off, you want to match your ring style to the base, i.e. Weaver or picatinny. Weaver rings will work on a picatinny base, but not the other way around. For a quality base and ring set (i.e. Seekins, badger, et.al.) you're already rocking the picatinny style. No issues there, the picatinny is a MIL-STD-1913 I believe, and the slot height spacing and height are specified and uniform. So if you set up your scope on a picatinny base with picatinny rings, and you find your scope is too far forward or back (eye relief) then you can loosen the ring rail screws and move the scope forward or back without drastically affecting the zero.
If galvanic corrosion is a concern, badger rings are steel, seekins are aluminum. Plenty of folks run seekins base and rings without a problem, but if you are in a high humidity area where corrosion is a serious concern, then you may want to be aware. Coatings on rings and base make this a nonissue for me, but I leave the coatings as is from the manufacturer. Good pieces are machined on a CNC machine; I won't be able to do much with hand lapping other than booger a good set of rings.
20moa on a base should work fine for your application. From a 100 yard zero, you look at roughly 37moa elevation to get to 1000 yards. The 20moa base will allow you to use the first 20 moa of adjustment that would normally be 'down' elevation on a flat base. The cost is neglibigle, and in many cases no change at all from a flat base.