I meant to respond to your post about tacking a lateen rig a while back but slacked off (and now the comments are closed), but I couldn't remember where I saw a good explanation for it. Anyway, I found it explained nicely in the "Sunfish Tuning Guide for Racers", and I copied an excerpt for you below. See the .pdf file for more info if you'd like.
A unique quality of the Sunfish is the fact that the sail is flatter
on port tack than on starboard. This has several consequences
when it comes to upwind sailing and tuning. In medium air
(five to 15 knots), the boat is generally sailed the same on both
port and starboard tacks. The ”mast phenomenon” becomes a
factor in light and heavy air (under five and over 15). In light
air, especially if there is any chop, it is important to avoid over-
sheeting on port tack. Letting the sail ”breathe” helps the boat
reach maximum speed, which is essential for effective pointing.
The fuller sail on starboard allows for tighter sheeting without
stalling.
Look, it also surfs.
Go my2fish!
