I think you're reinventing the wheel. I'd just machine a load tube to slip over the existing spindle and use the wide 5 type hub that's been proven to work for over 50 years under loads far exceeding anything you'll ever encounter on the road. Go ahead and waste a lot of time, energy, and money doing it your way, however.
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!