As a rule of thumb I always try to just make it a habit to design in a rectangular shape (wider than tall) when a hoodies are involved that way I can get plenty of leeway for design coverage if I want it. There are always those times though when they get thrown in after the fact. Happened to me the other day and had to output two different size seps. I would leave plenty of space for the ledge the pocket will create so I would definitively ere on the smaller size if I were you.