I was chatting to a wheel manufacturer at the Silverstone Classic 3 or 4 years ago. They were more than willing to replicate the S1 wheels in alloy or magnesium, if I can find their details I'll post on here. Incidentally the Factory told me that you can only change the wheels once, something to do with the relocation of where the grub screen goes into. Worth checking, sorry I can't help with changing to 5 bolt wheels but seems an expensive last resort option?
I understand this and had to extend or remake a groove but strangely I put my spare set on my current S1 and they all matched up
