I ditched the 16" factory alloys running 50+psi.
I now have 19",s with 245/45r19 tyres at 40psi all round.
I live up a bumpy stone track and the factory wheels/tyres and suspension made ride miserable.
My new set up is like night and day.
I was advised by a local company that specialises in Transporters, that, if running the van mostly empty, that the Cobra springs were least harsh compared to H&R and Eibach.