Sioux Cheif compression closet flange

I have installed a Sioux Chief compression flange inside a 3" san pipe which of course shrunk my inside dimension to less than 3 inches. My problem is I install a no seep No. 1 wax ring, but the plastic flange is too wide. Should i trim the plastic flange with a razor blade or is there a wax ring that would fit this closet flange? Any advice would be most appreciated.

You made 2 mistakes. You should never use an inside fitting flange on a 3" pipe. As you noted, that cuts down the diameter of the drain considerably. Second error. Never use a wax ring with the plastic funnel. These cause more problems than they ever cure. Even if you get a good seal, there is reason for concern because of the inside fitting flange.