Back in the 70's when we ran air shocks with big and small tires on F bodies I always noticed the crappy job GM did on the pinchweld under the rear splash pan because the rear of the cars were jacked up. Well those fugly looking pinch welds are still there on most of the cars and haven't gotten any better. They got bent on ice mounds in the north, rusted, repainted without being sanded smooth or stripped, and so most look worse than they did from the factory. I'm going to make a rear diffuser for my car and folks will be looking under there taking pics etc. so I figured now's the time to even it up and make it more presentable and finished looking while getting the whole tail section in final primer.
So I gave myself a guideline and used a 4 1/2" cutoff disc to cut a thin slice off. Then ground it pretty even with a 4" grinder stone, filed it straight, and got rid of the sharp edges.