You might also try Harken's rule of
thumb formula for mainsail loading:

ML = E^2 * P^2 * 0.00431 * V^2 / (sqrt(P^2+E^2)) * (E-X)

where
ML = sheet load in lbs
E = foot length of main in feet
P = luff length of main in feet
V = wind speed in knots
X = distance from aft end of boom to mainsheet attachment in feet.

I think the mid-range 2k SWL blocks will likely work for you.

-- Tom.


Thanks, Tom!


Robert
35s5
NY