Sailing the other day in strong winds, I noticed that angling the board back seemed to help on every point of sail, including hard on the wind. I had previously found better performance hard upwind by reefing the sail and leaving the board vertical. With too much sail out, angling the board seemed to help.
Another important variable is the presence or absence of the Mirage Drive. I sail with mine installed almost all the time, only occasionally sailing with it on the bottom of the creek. Though the blades will tend to feather themselves, they still create some lift far forward. It could be that without the Mirage drive, the whole situation changes.
Anyway, I've taken to just leaving my board angled back almost all the time. It seems to help, but I do have to say that I'm usually sailing with my wife. She always rigs the bungee to hold her board down and vertical. She's also pretty sloppy about sail trim and not so great at steering a straight course. I'm usually (but not always) a bit faster than she is, but only a bit. The AI is a very forgiving boat. Needless to say, it really makes me nuts when she's actually going faster. Shouldn't be possible!
I'd encourage you to read the wiki article
, if nothing else in case some of your customers are pilots...
The swept-wing also has several more problems. One is that for any given length of wing, the actual span from tip-to-tip is shorter than the same wing that is not swept. Low speed drag is strongly correlated with the aspect ratio, the span compared to chord, so a swept wing always has more drag at lower speeds.