Have a crew that's considering starting in BVI and heading straight to SVI. Do you they need to clear into USVI if just passing through the waters? How much of the BVI charter fleet is US flagged, and of those, do many have the sticker required for the ROAM app? Thanks for the help.

Unless things have changed in the last eight years you should be able to sail directly to the SVIs from the BVIs as long as you don't stop along the way (not even dropping the anchor for a swim). On our last trip we sailed from Jost to Culebra and did C&I in Culebra. Keep in mind though that if you do clear in at the USVIs you still need to do customs again once you get to the SVIs.

Can't help you with the second half of your post.

Charter? If so not all allow their boats to journey to the SVI.