20%!? Don't worry about it. At all. Seriously. I brew with 61% wheat, single infusion (well, decoction more recently) with no rice hulls, and no problems occur. Same with 22% rye.
I suggest you set a baseline by brewing it single infusion, then change only the mash schedule and see which beer you prefer. I think you'll find it doesn't change very much.
Well, decoction might, in a delicate enough beer.