I had some Boge springs off ebay. They were listed at -50mm.
Side by side with the std 16V springs they were much shorter. You could tell how strong the spring was
just compressing them with my spring compressor.
The ride was terrible, way too hard.
I put the std 16V springs back on and some shortened gas struts from
a german place on ebay. Much better.
I've used eibach on other golfs, polo g40's, Audi A4 etc.. can't beat them. The progressive windings
keep the ride nice.