40 would look okay, you should get 2peeps in the back without rubbing....however!!! you can get 60mm drop with saxo springs, and that would look the poodles pebbles
In all seriousness tho, you'd prob (with 60mm drop) loose full lock, but you can compbat this by gettin your "arches shaved" costs about 100 and solves this problem..
Get some Eibach Pro Kit front springs...30mm drop. Anymore will make the car less driveable over bumps.
And don't forget if you lower it too much you wreck the steering/suspension geometry and you can get bumpsteer.
Bumpsteer is when the geometry of the front suspension changes and as the suspension compresses it actually changes the steering angle therefore we have bumpsteer.
If you drop the car a sensible amount you'll be ok but at silly drops the lower wishbones change angle too much and that's when it can create bumpsteer.