Looking to setup a gravity brew system. Going to use a 10 gal cooler MT and 10 gal HLT. My question is do I get a 10 gal BK, 15 gal BK or a 20 gal? I know with a 10 gal the most I will be able to do is 5 gal batches. I know there are other variables that go into everything but should I do a 15 gal BK or a 20 gal? Or is a 20 gal too big for having a 10 gal MT and HLT. Thanks for the advice.