Why not make it less stressful/expensive and do this?....
Take the 7:30 AM Sensation ferry from VG to RT
Hop the 8:30 AM Aquatic rentals RT-STT??
You will clear in STJ and make it into St Thomas with plenty of time to make your flight and probably even grab breakfast.
We come from VG into STT on our trips (our flight is at 2:30) and we have never had a problem and always have time for a hearty breakfast in town rather than the horrible airport choices. Other benefit to the earlier ferry is that they are usually less crowded and therefore you can get through customs much faster. Our last trip we blew through in 15 minutes.
