Starboard are 1 they have just got the old Evo shape and stuck 4 fins on it. Seems like they couldn't work out how to make a good twin, it got a bit of negative wrap and ceasing it after 1 year seems to confirm that. I guess a few people are feeling ripped off by them.
Jp is the other one I know of. Theirs just looks like their old twin fin shape but with 4 fins in it. It looks nothing at all like the one that their sponsored Kauli uses windsurfing.pro/ .
Saw some pics on the net of a Tabou quadbeachtelegraph.typepad.com/beach_telegraph/2009/06/tabou-quad.html
I'm praying to the old man that Quatro will bring out one as they use proper wave rockers not bump and jump rockers. Plus they had the most experience working out if Quads are any good or not.