What kind of "10-speed only hub" is it?

If it's a Dura Ace, you're probably stuck with it, but if it's an Ultegra hub, you might be able to change the freehub (mind you, ready-made Ultegra wheels are sold with a 10-speed only freehub core while separate Ultegra hubs are sold with an 8/9/10 speed freehub core.

If it's a non-Shimano hub, you might check to see if you can change the freehub cpre for one with shorter splines.

P.S. Don't shorten the splines of an aluminium freehub core. The splines are deep for a good reason.