Now that my trip is done, I just want to provide a report. I arrived at the airport in BOS early enough to switch my reservation onto the 1155 flight to JFK. This change was confirmed at the ticket counter (with seat assignment) and I did not have to deal with standby. My luggage was delivered promptly at JFK. I had to take it and kill about an hour by riding the Airtrain before the OS check-in counter opened at 1425. On the way back, I had to claim my luggage at JFK anyway to clear customs, and took the Airtrain over to T6 to check it for the JFK-BOS leg. All in all, I had no problem making my connections and could have made it comfortable even with delays on either end.