I went with three 20's and a 40. I get them filled two at a time and can be assured of brewing and grilling at all times, but way back when I swapped out the grill tank on a pretty regular basis to salvage the brew day. Hopefully your hop schedule worked all right. I think for all but Pilsner malts you can get away with a shorter boil, if you use a first wort hop/hop stand or whirlpool hopping as the only additions.