ok quick sanity check:
balancing weight:
two guys on the wire =2*60kg
100kg cat =50kg
beam: 2.3m
mast height: 9m
center of sail force: 40%
resulting sideforce =((2*60+50)*9.81)*2.3 / (0.4*9) = 1066 N
board height in water 0.6m, board width 0.2m, board area 0.12m²
aspect ratio AR=3 and hence lift coefficient 2*pi*AR/(AR+3)*1.4 = 4.4 per rad = 0.077 per deg (factor 1.4 for hull effect)
Assuming we travel with 16 kts = 8m/s and have one board down:
board cL=1066/(0.5 *1000 * 8² *0.12)=0.28
board alpha = 0.28/0.077 = 3.6°
slowing dowm to 12kts:
cL=0.49
alpha=6.4°
cL and alpha would be roughly half, if both boards are down and on a boat with weatherhelm, the rudders take some of the loading.
A 0,60 x 0,20 cm board seems small, but not too far from reality. The calculation considered 16 kts the capsize speed. 18 kts makes more sense to me, perhaps more. Also, I'd expect the speed reduction from 16 to 12 kts to be accompnied by a sifnificant reduction of lateral force.
Note that the daggerboard, rudder and hull contribution to lift must be all considered together for this calculation.
While the daggerboard is perceived as "the" source of lateral lift, the rudder usually operates athigher angles of attack, generating more lift per unit area. The hull is a low aspect ratio foil, but its surface is big compared to the other foils, making its contribution relevant as well.
All considered, the sanity check seems to indicate that 2 to 3 degrees make perfect sense.
Thanks!