5S gearing in a Savage Flux

[Ascender]

What I'm looking for is really the right range of pinions to start with. I know 16 is going to be too low, and I know 21 is going to be to high, but that still leaves me with four options, and that's discounting the guys who insist that you have to gear up with more cells, and insist that you HAVE to use the 25T with 6S or your truck will obliterate the Eastern seaboard and plunge the world into nuclear winter.

I'd like to run this weekend, and I don't feel like spending $40+ on pinions just to have them all there to test.

BTW, I should add that my truck is about a half pound heavier than stock, and is primarily a basher.