I'm totally different on my boat.
I totally ignore the telltales when setting mast rotation and just adjust my mast rotation to get my leech to stand-up/fall-off properly. Mast rotation has a huge effect on this. I'm more geared to get proper twist and getting the flow to detach properly from the leech. If I don't do this then my boat "hangs-up".
Mind you the cut of my sail at the top may not be what it is supposed to be. I'm sailing with a Redhead mainsail. I think you have one too Pete. On other F16's fitted with ullman or glaser sails I think you can look at other things as suggested by the others. On the Redhead sail you have to check first whether you twist and draft profile is correct or risk stalling the top early on.
Wouter
You may be right Wout. I've been setting the rotation as suggested. Sometimes it works, but often my performance to weather is way below everyone else.
