Frame Rail repair "cap"

I have a car used as a pace car at a roundy round, turn left, dirt track for decades. The wet dirt caused just the lower part if the rear frame rail to rust, the sides were fine. Weird.
I fabed some heavy 10 ga sheet into "L" shaped pieces and welded er up! Solid as brick poop house! I know the 10 ga was over kill but it was the scape I scored.
No matter we are doing, the rust has to be cut out and go from there.