Have you already machined the wheel down as much as possible yet?

Also put on a narrower tyre, 235 is well wide.

I had the rear arches rolled on my old sapphire to stop them cutting into the tyre but at a low height and with 225 wide tyres on on acceleration the tyres still rubbed on the outer edges inside the main wheel well.

Don't forget track day tyres have a squarer shape to them rather than normal road tyres so always come up a bit bigger.
Also your rear wheels are gonna have less camber being on a 6 degree beam

Cheers Paul