I'm considering buying the Aeris Velocity as a gift for someone who wears a men's 10.5 shoe and wears a 6.5mm boot when diving. I'll have to guess at the size since I can't find the fins locally. Sizes for the Velocity are S/M, M/L, & L/XL. I'm guessing that the M/L is the correct size, but the L/XL may be close as well. Anybody have an idea on the best size to order?