most people cut inside and outside rows off there front tyres no matter what size the rim is, if you're suffering from grip roll then cutting the outsidespikes off will definatly help you out and still maintain the frontal grip you require.
i had the same problem at bury this sunday just gone and cut the outisde row off, still had the same issue, although it was driveable. for the final i cut all the inside off too as i saw the grip was really coming up and my car improoved imencely. i was on pace for 4th in the A final with my final time before i broke my car. 100% improovement