If your sail top was wide as on a wing it would possibly have some merit but as most sails have an angle substantialy less than 180 degrees your stallpacck would have to be as wide as the tip of the sail = 0.0mm/0.0" .Never the less I would like to see one of that width constructed and full colour photos of its construction process posted here[}:)]

Jeeeeeesuuuuus! TP1 I's gonna come over there and Shove your head fair where the son don't shine.

Those wheels are starting to get to me. I am beginning to think some are Deaf in the Eyes and Mind as well. They aren't Hearing what is being said or like yourself just Stirring the Pot. Bleedin' Sod.

What are you saying about the Stall Pack/Truncation thought???

Given that the Sail top/Tip will be 350mm and is capable of Flight all-be-it perpendicular the theory remains true, however the gained eficiency is what comes into questin as the speeds are not as high as those gained by powered Aircraft but are Greater than those of a Soft Fixed Wing/Hang Glider and both craft have or still use the same technology.
If there is a flying surface then the Angle of attack will determine whether of no there is a pressure gradient therefore the Higher pressure will try to escape to the lower pressure area thus attempting to negate any lift gain = inefficiency. If this pressure lose can be negated then the Flying Surface should become more efficient?? Look carefully about you the next time you go out Land Sailing and you will note that there are many different sail formats about you some with the Leech Edge passing up around a batten before dropping back to the Luff Pocket to others who's leach rises and changes direction around each Sail Batten until reach in their Luff Pocket. So in some cases, were a Stall Pack/Truncation would be of little use where as others the reverse could well be true.
I am no expert on Aerodynamics but I do have some knowledge, of which I would like to increase as our chosen Sport relies on it. Proper use , as with Greenbird, will increase speed capability, lower drag amongst the benefits.
Least ways those are my thoughts.
Ron

Who're you call in Fat Head Boy?????
Well now I wasn't to know that. However it is only a little fat head 350mm or less but there is some Luff pocket design change as we are hauling more tension on the top 700mm. Anyway that is an easy prove. I will have to make some sort of Smoke generator and attach it to the Mast Top and observe the effects in wind.
What is more I like to experiment..
Ron

Don't gotta experiment with them. Doctors are doing enough of that with me as it is.
Ron

Thanks,
It is all food for thought. Before I fit anything I will run some tests first, Heavy Angle of Attack first.
Ron