Guys you really should be making sure that there is 1.5x the thread diameter, to be super safe, so 18mm of useable thread. Probably a bit OTT but I wouldn't drive on less than the stud diameter.
As for spacers putting extra strain on the studs, thats nonsence, if the studs have the correct ammount of thead in the nuts they are just as safe, it is the friction produced by doing the nuts up betwen the wheel and the mounting surface that keeps the wheel in place. Check out my blog, fitting longer studs is not hard, though I did need to relieve the back of my drums and discs slightly to clear the longer splined section of the non oem spec studs.
MPH sell the correct longer studs. I sourced mine from I think Performance car parts e-bay store, check down through the mechanical servicing and modifications section and you'll find a thread with the link.
There can be problems with centering the wheel when using spacers because it mounts the wheel out past the hub spigot, but this is lessened by the fact that we use tapered nuts so these center the wheel instead of the spigot.
I'm currently rolling with no center location on the wolfies. There is a little wobble over 70. I'm going to turn up some spigot rings when I get time.
You can also get hub centric spacers which have the correct bore for the hub on the rear, and the correct spigot diameter for the wheel on the front so that they keep the wheel centered.
