i just have 1 install, with all the latest stuff.
i have 4 cars.wads (1 normal, 1 for france, 1 for silverstone and 1 for Indy).
i make backups of the main cars wad when i want to install a new car, just in case. i try out new stuff in 1 of the wads, then if its good, i put it in the other 3.
never had to re-install the whole game for over a year.
i keep 1 big folder with all the updates i have ever used, separated into seasons, then into cars, tracks, helmets etc. and i have another folder called "CarsInWad" so everytime i install a new car, i update this folder, so i know at-a-glance whose cars i have installed.
RIP Jules, never to be forgotten. #KeepFightingMichael