My biggest spin at 3S was when we went testing at Alfa 75 after upgrading the front brakes and installing a balance valve. My mate took the car out first, then came back and told me to have a go.
I did a couple of bedding-in laps then gave it some beans on one of the straights and braked really late for the corner - at which point the car swapped ends instantly.....
I came back into the pits and opined that there was perhaps a little too much rear end bias........to get the reply - "Yeah, I thought that"..... but of course he never mentioned it to me....