I read through the entire website and found a few things interesting, like this. . .
The fleet will sail into the Hemingway Marina and clear Cuban Customs and Immigration prior to pulling the boats out of the water.
quote source. How? Inquiring minds . . . This sounds very difficult to do with our boats if they really mean to clear customs on the water.
If the organizers are already in Cuba, they could coordinate the process. I would think you set up a RIB or similiar to meet the boats in the marina, tie along side like you are rafting up and take care of business. I would think this would be much more difficult if done outside of the marina in open water. I'm sure the organizers (on both sides) are much smarter than I... ;-)
Of course if they pay my way over, I could expidite the process for them.