Saw this in Canadian Biker, I think..
A guy in Calgary , cafe'd a CB 650. He widened the rear wheel to 8.5 inches and runs a wider front rim I believe. Not sure if he would do more said it was tricky.
Apparently part of the cross section is hollow, was not aware of that.
I know Kosman does widening for around 450 bux, be good if someon in Canada did them.