OH Yes! That is the case as I found out last week.. I believe up to three times the wind speed.. I've decided to not go there in 40k winds.. It can get real scary.
Ron

Yer Right! Gizmo, It is fascinating and tends to feel odd when a wind vane mounted up front disputes the actual Wind Direction or the Tell Tales hang limp and you are charging down the beach.

Lord Admiral Nelson. Yes Nelson lives up the road from Wynyard. He was stunned when he saw what the Occam's Razor was doing in comparison to the wind, to quote him "I had No Idea". I was stunned to see what a difference flattening out a supposedly fast sail. To quote me "The added power and speed is Awesome". Oh! By-the-way. Nelson is the other Land Yacht sailor who gets around Pegg's Beach.
Ron

How far back along the chord are your telltales?

If they're in the front third then the stagnation point might have moved behind them. The wing could have been oversheeted as well.

similar thing happened to me as I sailed into the lee of the dunes, as I slowed down , luffed her up a little and bango!!! off she went again, at a little slower speed.

this set has polished all the rough stippled surface off, yet the salt was really smooth as it rained on friday.
maybe go for13kg?.
a good check is to see if the yacht will self steer upwind. if it goes down wind,move mast forward till it almost stops?