Maybe I've been too inattentive to the schedules, but my understanding is that there's no direct ferry from STT to Virgin Gorda, other than Speedy's which runs only two days per week, with two departures on Tuesday and only one on Saturday. https://www.virginbookings.com/ferry/st-thomas-to-virgin-gorda

While it's great that unlike other ferries, with Speedy's there's no need to take a taxi across St. Thomas so as to get to Red Hook, I'd rather not be limited to two days per week, and I like the idea of getting to Virgin Gorda more quickly (and on my own schedule).