I purchased Annie with 16mm genoa sheets fastened to the sail with a cowhitch/larkshead. I replaced the sheet shortly after purchase and found the knot was rock solid...no chance it would slip at all. After an hour with a marlinspike I gave up and cut the knot. I used a cowhitch/larkshead on the new line and it held fine, no slipage. I untied the know after a year because I didn't like the way the line looked like it was bending as it left the knot under load. I cut the line and used two bowlines, which I still have now.
The bowlines do seem to catch on the forward lower shrouds and if the sail is allowed to flog during a tack the weight of the two knots seems to make things worse.
Take home message: cowhitch is smother, does not seem to slip once set, but I am concerned about concentrating force on a small point of the line. Bowlines seem to spread the stress across a larger area of the rope, won't slip and have the benefit of being two separate sheets in the event of a failure near the knot/sail.
SV Annie SM37
Le Marin Martinique