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.

Cheers,

Klaus