I wouldn’t worry about curbside. FC customers have access to SkyPriority check-in. In Terminal A, this is to the left of TSA. Most pax get dropped off at one of the first sets of doors on the departures level, where main checkin is, so it always seems pretty hectic on this side, but once you walk past TSA, it’s a lot less people. I don’t think I’ve ever waited more than 2-3 minutes in the SP line to drop my bag off a BOS.