360 Wheel bolt to stud conversion; correct lengths

Has anyone measured the length of wheel studs needed to replace the bolts?
Studs seem to be measured from the shoulder. Most shoulders are approx 8mm but I do not know how far the shoulder extends past the hub. I guess 6-7. Close enough. Then I need to figure out what length threaded surface I need to get enough turns on a challenge wheel.
Open lug nuts, so I have some wiggle room.
I can't be the first to so the math, but I can't find any threads on this.
Advice, please!
I'm not near the car, otherwise I'd figure it out on my own.
I'll post back here, if I can find an answer elsewhere.

Thanks, in advance!

Man. The ads on this site super intrusive. I almost gave up posting this.