69 Camaro rear tire with DSE min Tubs

[srode1]

I'm trying to decide specs for a set of Forgeline wheels for my car using a tire measuring / set up tool. The I have a 69 with a Currie rear end measures 54.75" flange to flange with brake hats and DSE mini tubs and Ride tech 4 link. The top center of fender is 14.75 on both sides to the inner fender. When I set the suspension full compression things get pretty tight using a mock up 335/30/18 tire with the tire measuring set up tool set a for a 12 inch rim.

Tight spots - There's a little bump in molded into the DSE tubs in the front sidewall area both sides that is about 0.3 inches of clearance when I set the tool to 5.75 inches of back spacing and the axle level compressed, that's the tight spot on the inside, I have at least 0.5 inches everywhere else. I moved it in a bit because at 5.5 inches full compressed is hitting the lip on the quarter (not rolled yet) and this gives me an 1/8 inch of clearance at the tight spot which is the top rear of the tire to the quarter lip.

So I'm debating about using 11.5 inch wheels to get more clearance and rolling the lip on the quarter. The other consideration is with 11.5 I can go with 315 or 335 tires and stay in the recommended range of rim width. Curious how much is reasonable to gain in clearance rolling the lip on the quarter and if 11.5 inches and 335s will have noticeable impact on handling on street or auto cross or road race course. Thoughts?