my W, 51, 02, 03, 53 & 54 plate were all 17mm hex with a torx centre lol!
bit of penetrating fluid on the bolts from the underside of the car, leave for 5 minutes and remove, either that or impact gun!
once removed, refit the bolts or you will have a leaking car lol!
Yeah I did refit them, would be awkward if on a wet day I found that everything in the boot had be sprayed with a lovely coating of we mud