Ryk
My headsail size is determined by the best VMG (not speed) I can get.
Many times a too big sail plan will have too much leeward slip when
going 'up' ... drops VMG catastrophically. Its my belief that the
high end race folks match the SA to the optimum VMG for best
performance upwind and thats why it seems that over the years the
headsails are getting smaller and smaller in LP. Such is also
'easier on the rig' as a BIG LP heasail needs lots of winch pressure
which ultimately reacts to sag off the headstay to leeward, ...
requires more backstay tension, etc. etc. etc. etc. etc.
:-)