It's a modification of Phil Bolger's Brick - the Puddle Duck Racer. This one was built by my friend and occasional forumite Paul Helbert, and modified a bit further with Michael Storer's ideas. We took her out to a (relatively) local lake yesterday, and it was a bit windy.
Impressive how well an 8' x 4' rectangle can sail! But, yes, the square bow does indeed present some issues in high winds, and there is zero warning before the whole bow starts to go completely under! You have to keep your weight further back than I think is ideal, but she will definitely scoot in the right conditions.
Here are some short vids, and yes, that's me.