RE: A real STARTBOARD LONGBOARD???
I think the two boards have more of a real Stand up Paddle heritage than old windsurf board heritage. So, no centreboard make sense. They will probably not be upwind rockets, but judging from how Jeff Hendersson and Giampaolu Camarrotta have been able to move around the breaks in super light winds on their longboards, I would say it far from "drifting" either. The long water line and the shape in general probably gives as much lift alon as a small centre fin does on a shortboard.
BTW, see Svein talk about the boards with Giampaolo on his blog: