I'm not sure exactly how much I have lowered my car (mk2 Driver +20mm higher over a gti). Around 40-50mm roughly. When I fitted my coilovers I left the height at how they came in the box. Which happened to be about 80-90mm, didn't look v good to me. I kept it like that for a few hours and a giggle but it's just not worth it when you felt how harsh and crap the ride was + you couldn't full lock, go over speed bumps properly, carry passengers + girls just get pissed off with it etc etc. I think for practicality no more than 40mm for a gti.