Need to lower the car - Please Help!

[vw754]

I need good quick advice, a4 tdi 1.9 2002.

Going to lower the car using springs only,decided to go for koni as ive heard they are good.
Was going to buy jamex but heard tooo much bad news about them,i.e uneven ride height/cracking etc,etc.

My most important question is how much can i lower the car without problems? i was told if i lower too much driveshaft would rub/foul the anti-roll bar

Some say upto 40mm drop is ok no probs,some say no more than 30mm,who's right and who's wrong? i need to know this a.s.a.p please help,thanks