WOW....FINALLY!!!
All I have used is a jig saw. Use blue tape on the paint before cutting. It cuts easy with the right blade and I used a die grinder with a sanding pad to just soften up the edges.
We have about 1.75" clearance on the top of the front and about 2" for the rear. We cut everything short and then had the jig saw on the pit wall for small modifications once we hit the track. The rear tire vertical walls are pretty tight to the tires less than and inch in places. We have found the rubber leaves nice wear marks and its easy to continue to trim until correct. Dont trim to much! We had about 3 or 4 pit road check and trim sessions before it was right.
Good luck! It was pretty easy!