Just a thought that has worked for me in the past. There are usually one or two "welcome" ambassodors at the ferry dock helping with your check into the BVI. Ms. George is super. Just ask one of them "immediately" if you will be able to make the 4:30 to VG. Most likely she/he will take you to the head of the line and even hold the Speedy ferry a few minutes. It helps to look confused and pathetic (I'm good at that).