Vw - Porsche adaptors

Hi guys,

could anyone save me some time as I'm sure it's all been done before.

i have been messing around with different set ups for the ride height for ages now and have finally succumbed to a set of coilovers to be able to get the stance I want in terms of height.

I have a 1989 Karmen convertable on coilovers + D90 6j all round porsche alloys.

my question is this

what size adaptors will work best ?

surely someone has done this and can just say "yep, use 30mm on the back and 20mm on the front"