Didn't take much. Just drew a line from a logical spot on the rear to the back of the front lower fender mounting bolt. This made the line straight. I left extra so I could bend a new 90 in it instead of having a sharp edge. This allows the inner plastic to stuff back in too.

Then after a bit of stuffing and turning I saw the lower part of the bumper still kissed the tire at full turn. I trimmed just a tiny bit off, a pie shaped slice opening up about an inch on the bottom.

These are chunky 31s too.