325 - 285 = 40
35 - 25 = 15 / 2 = 7.5
40 + 7.5 = 47.5 pund corrector weight.
Crew + corrector (285 + 47.5) = 332.5
Best place in the hull just behind the main beam(if you have access) half the weight in each hull. Attach with line to dagger board well.
Second best is at the mast base attached to the from cross bar.
Soft Dive weights are best. Cheap alternative is lead shot gun shot. These will not damage body or boat.