I flew JFK-BGI-JFK on a DONE4 last December, but I stayed a few days so I cannot comment on turnaround. I figure though that if you don't have any checked luggage it shouldn't be much of a problem, as I got through immigration quickly. Waiting for the bag took a bit longer, but not as long as in emerging markets airports (like LHR). Of course, my outbound flight was delayed by six hours due to some defective part or other. Anyway, even with checked luggage I think you can make the turnaround unless you one those 747 came in just before you.