I wear 14 shoe size and thats a bit small, but most 15's seem too heavy....so I have messed up toes.
In my oppinion, a huge part of the size of bindings is knowing how to get them on or off. I have some old 3060's that I use soap to get into and then to get out I just put the board under me and jump, I come right out. I've seen people with size 10 shoes not be able to get out of my bindings for a good 15 minutes....Retarded.....I hate watching others mistreat my bindings.
That being said, my bro had some XXL highbacks that were incredibly loose on me, also XXL Ultras I was sliding around like crazy.
Many bindings are adjustable anyway. Go to the store, try on as many as you like, find the closest, take it home, do the heat soak thing, and if you want more, adjust them.