In my neighborhood, I could find half a dozen machine shops who would be glad to do that little project for $50.00 or less. "Your mileage may vary". With just a little more machining time, with the same setup as the hub modifications, I can widen the 3/8" belt grooves to accommodate belts 1/2" wide, without compromising the integrity of the balancer.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!