I ride 10.5 dc boots (2011) with a 152 subzero and have no drag at all.
I used to have some bulky burton boots (2007) 10.5 and i also had no drag on those as well.
You will be just fine. It's a great board, i wouldn't count it out based on the narrow waist width. Part of the reason the Subzer has such a narrow waist width is cause it has a small radius sidecut in the center and a larger radius sidecut under the bindings.