Even with the downhaul completely off the top would twist off very easily in lightish winds. The Ullman sail that I sailed with on the Blade was made by Ullman USA and is different from Zuccoli (Ullman Italy).

We layed the boat flat on the beach with the mast horizontal and felt the "springiness" of the flap. It was extremely easy to have it twist off. Even under gravity alone it would twist off.

Several "solutions" were tried over a longer period of time including different battens and none improved the behaviour. Actually, the original battens and setup proved to be the best given the limits posed by the mainsail design itself.

Again, it does really seem this mainsail is rather good as a singlehander sail. So it is not bad in any way it just "different" then what you want when sailing/racing 2-up at 140 kg.

Wouter