Or fit some wooden spacers if you don't want your bum scraping on the floor.
??? How much seat membrane to floor clearance do you have? The later cars such as yours have nearly 3" as standard? Raising the seat without supporting the runner frame will cause it to bow and your back to square one and if you fit full length plinths you need to drill them to clear the bolt heads so why not just drill the floor board, it's hardly water tight is it, have a look at the hole around the spring shackle.
