Build the area up with epoxy and basically build yourself an epoxy edge. Lift the base up and wet out that area to to keep it glued down. It might take a few coats but once it's a little bit bigger then the sidewall and base, let it cure fully, and then sand it flush.
It seems ghetto but it's a repair I've talked about with a few other members and really it's the best option. If not the edge section you put back in will just keep blowing out,