ok some real life reports about stiffness:

one or two years ago, I tried to use dyneema for the shrouds. Because of the creep, I never could setup the rig as tight and stiff as with wire. It felt different, but it wasn't slow. I run the same speed, the same vmg. But the stiffer rig felt much better, more precise and predictable.

Some years ago, when I did a load of road cycling, there was a huge trend to stiffer frames claiming for a more efficient transmission. I had a stiff bike and a very flexible one. You could really feel the difference, but I could never messure any difference in speed. Funny enough, some time later, there was new trend to new super light weight wheels with 16 or so spokes. Everything you gained with the frame you lost with the wheels. Most people still was convinced that the "stiffer" bike was faster.

I remeber some peolple quoting to must have a low stretch sheet material, and now on some A-class the trend is to use a mid sheeting, supported by the floppy trampoline...

Wasn't the mast section of the Fx-1 too stiff to tune the sail adequately for a single hander? Never sailed one seriouly but was is your expierience with it?

Cheers,

Klaus