wheel to fender clearance

If you have 1/2 inch with 28s, Ima thinking your ride height is higher than some of us. Have a couple of 200 pounders climb into the backseat. If it doesn't touch, you are good to go.
I had a quarter inch with a lowered ride height, and it was good. Under full power, the rear end will try to come forward, but on the street traction is hard to come by. And I have poly bushings. So for me 1/4 " was good.