Had mine lighten to half the weight of standard!
Main
problem I found was when you rev it high while idling it took about 2 weeks to rev back down to an idle rpm.... this means it takes more momentem to get it to spin up.
Lighten allows the car to rev up quicker, main disadvantage is that you lose bottom end torque but end of the day it's a 16v so you need to rev it to get the best out of it. Another one is the old theory of going up the hill flat out... with a heavier flywheel the momentem of it spining (stores energy) will aid the speed but with a lighter one momentem isn't as much so your speed will drop.
Tbh none of them reasons have effected me since I had it done, only
problem I found is pulling off you'll need to rev a bit more.
I mine down by a local guy to me and he's big on club gti for rebuilding gearboxes and lightening & balancing flywheels, "hotgolf" look on the sale section on that forum he's usually selling some. Golf G60 flywheel is the same as the
Ibiza so look for that to!
Do a search, I asked a simlar question a few years back.
