There is a very good statistical analysis on the web:
http://www.geocities.com/f16hpclass/F16HP_optimal_crew_weight_analysis.html
I recommend to completly read it, because the author actually made two analyses. One simple normalised time to finish over weight (light boats are better even in strong winds). In a second attempt he realised, that the good sailors have in general lighter boats. He compared than the relative performance of each boat in different wind conditions and found that light crews/boats perform better in light wind and heavy crews/boats better in strong winds.

Another proof is, that top sailors are in general not lighter than average and that female crews (which are lighter in average) are not the faster sailor in average.

If you can't use the benefit of a heavy crew in strong wind, than maybe because you don't have the right heavy weight trim for your boat.

Cheers,

Klaus