You are a member of the forum now. There is no private group here. At one time there might have been but that died a long time ago. The Facebook page does in fact require you to share your vin to join. They are exclusive to NC1 owners. If you sell your car you get thrown off the forum. My recommendation is participate on both. Glad to have you with us, it is a great car.
I participate on the Facebook page, but like the organized way discussions occur on NSXPrime. Both are good in my opinion. There are probably 8 plus owners of the NC1 who participate regularly on NSXPrime.