In my experience on the F16 from 280-340 crew weight provides no difference in performance over pretty much the whole wind range. (Racing 5-20 knots A drifter is pot luck anyway ususally and +20 starts to become survivial for a lot of people) This is 2 up crew weight as that is typicaly how I sail and have run the full range of crew weight.

The boat looses some "feel" in responsiveness with more weight but finishes just fine. Over 340 you may suffer a little in the very light stuff and under 280 you can quickly become over powered. Anything within 20-25 lbs of the main range and performance is still within a range that the finishes will be dicatated by the skill of the crew.