I did have a hand in repairing the car Eleanor Chubb used to do the Toureag trail in 2007, it was very tired and quite rotten, I don't recall a lot of strengthening in the car beside the roll cage (which I wasn't too sure was upto it). I welded som stronger 50x50 rsa down the sills and to the cage mounting points, and added a crossbar under the drivers feet braced to the chassis, although it must be said, most of this was simply to hold the shell together as it was a state than actually make a good shell stronger.
Still, have some pictures.
