Rolling Fenders With Rolling Tool & Sure Grip

I have a fender rolling tool that I want to use to flatten the inner lip to give more tire clearance. All the instructions I've seen show to mount the tool onto the hub and rotate it back and forth to slowly bend the lip. My issue is I have a sure grip rear that won't let me rotate the hub with the trans in neutral.

Those with SG rears & have used this tool; how did you do it?