Looking at the speed difference of (roughly) 9 knots upwind (6.5 knot vmg) and 24 knots downwind (vmg 20 knots) it looks to me, as an engineer, that the upwind is by far the most important leg on these boats and that 5 % additional performance on this leg is worth any "over 15 % performance hit" on the downwind legs. ESPECIALLY when these boats are width limited. The latter point would also favour more efficient rigs and masts (bethwaite squarebacks) then the grunt rigs (round tubes and less earodynamic efficient) they feature now.
How can this be a good idea?
5% gain on 9 kts upwind gives a speed of 9.45kts (so a .45 kts gain). Not much
15% loss on 24kts downwind gives 20.4 kts (so a
3.6kts loss).
Now unless the boat is having to sail a LOT higher to get this speed(which is not mentioned above), I'd suggest the "slower" upwind boat will still win around the course.
The numbers just don't make sense here.
