Thanks so much for the information. To play it safe, we booked American Airlines through to EIS so that we don't have to retrieve our checked luggage and then go through security. One of the benefits of doing this is that Seaborne, Cape Air or whoever will allow whatever bag limits that AA allows. Because we are traveling Business, the baggage allowance is significantly more than the smaller carriers on the SJU-EIS portion would allow without paying additional fees. I don't want to start or end my trip with stress so this seemed like the best option since we are checking and not just going with carry on.