ST165 spacers on 7th Gen wheels

I have some stock GTS wheels off a gen 7 Celica with 205/60/16 tires and they rub the rear suspension over bumps. What spacers have been tried and have worked?

What part of the suspension is it rubbing on? Tires sizes vary slightly from brand to brand and model to model, but I'd measure the gap from the tire to the fender (horizontally) and get a spacer slightly thinner than that.

I've been messing with it all day, and I think it's actually rubbing against the rear bumper or the two bolts that are there with the bumper, also I don't exactly get how it can rub against the suspension perch because that's where the spring is and it shouldn't contact there at all.