We had one couple use IC (it was cheaper than Seaborne) in October and no issues. We all have carry ons and we didn't have to leave the terminal from a Jet Blue DCA to SJU flight (its usually on the way back for us that we have to go out). The rest of us did Seaborne and what was nice is they had there own customs center on the way back and the gate for departing was right where we deboarded from DCA. This turned out to be good because Seaborne had moved the flight up an hour at the last minute and didnt tell us. So connections were done to both Seaborne and IC in under 30 minutes which has been our norm going in. We do have global entry which includes TSA precheck...

On Saturday 5 of us go DCA to SJU and arrive 12:46 to catch the 2:35 IC flight and on Sunday 4 more do the same. I can report back if you want....

I personally think you will be fine.