I wore 7 (ouch), 7.5 and 8 and on a Coda with a 250 waist it was fine. Looked like baby feet on it.i downsized to a size 8 in boots this year and most of my boards hover around the 245-250mm range. i think youll be fine in a 10. either way you already bought the board, might as well just ride it and see what you think personally. another thing you can do is just mount up your bindings, strap in your boots, and just look at it. should be easy enough to tell if its too wide/not wide enough.