First let me say that I'm basing my advice on having sailed from Virginia to the BVI three times and from St Thomas to the Bahamas
& Virginia once, and St Thomas to Florida
once. But even though we departed from a more northern port, I believe that some general principles apply if departing from the SE U.S. coast...
1. Watch the weather to see when the next frontal passage
2. Get safely across the Gulf Stream in the light SE to S winds that precede the front, motor-sailing due East, if necessary.
3. Ride the W/NW/N/NE winds that accompany and follow the front. Even if the winds are strong and gusty (35-45 kts) you'll be OK since they'll be behind the beam.
4.Watch the GRIBs and WEFax charts
to plan how much southing you can get while you're getting in as much easting as possible. Do this and adjust twice a day if possible. Have someone aboard dedicated to accumulating and analyzing the weather data and applying it to routing decisions.
5. Motorsail when the front blows out, unless you're lucky enough to have it blow you through the Horse Latitudes into the Tradewind belt.
Your proposed aiming point close to Bermuda
before turning south (the yellow line, below) is the "conventional wisdom", but in recent years most of the hundreds of boats in the Caribbean 1500
and many non-participants have sailed close to or just above the Rhumbline from Virginia to the BVI (the red line). That has been our experience as well, and we experienced the frontal passages described above and were able to take advantage of them.
The point I'm trying to make is that if you can ride a front/motor-sail out to about 29.7N 68.7W (the green line), you can lay a course to St Martin
and make it on a close reach, if the weather is "typical". Of course, Mother Nature is famous for throwing curve balls in the weather department, so you could see some weather that might force a different plan (better or worse), but that's why you need to have reliable access to weather forecasts throughout your passage. Note that sailing the green line vs. the yellow would save you a couple of days.
Another possibility is to link up with Herb Hilgenberg via SSB
or hire a professional weather router to create a plan for you and to send updates via email
or sat phone
Hope this makes sense...