Appropriate Wheel Offset for 18" Wheels?

I just moved the wheel over on the passenger's side. It seems things are slightly shifted toward the center line of the car. Without spacers, the tire was rubbing on the leaf springs. With the 0.200" (+5mm) spacers I had about 1" to the outer trim and 0.25" to the leaf spring. I took another look at the wheels, they're 17 x 8's and I think I measured them to be about 5.72" of bs which would put it at +30mm. However, taking a closer look at it I think I'd have some rubbing issues on the inner bulge of the wheel well. I'm going to need a little less offset and maybe I should just step down to 265/35/18's. How much is ample tire to outer trim clearance?

Odds are car isn't going to make it to Fall Fling. I just have way too much school work.