Also JFK 7 has a seperate area for concorde check-in AND security. If as the above post mentions, you have to leave airside to get to T7 then its to the extreme left as you enter. As they only have 100 to check in approx 3 hours the queue should be OK. They are just as zealous though in their checks.

However, I would strongly suggest an earlier connection or overnight stop in NYC. How often are planes delayed for all sorts of reasons. Even an on-time flight might drop you 30 minutes late if the landing runway that day calls for a long taxi -then you are being the timeline already.

Personally I would not have risked missing my flight for anything. I would have camped outside T7 the night before if it had been allowed. My advice -take no chances.