I dont remember what line we used there. It was some synthetic line (4mm, no uncover, silver colored) but I do remember the need to tune them to make the lower part of the jib set properly going to windward. Lining up the spi pole so it was straight and perfecting tension and length of the lines was a chore. The hulls also flex to a certain degree, so you rarely get perfect trim on the lower part of the jib even if perfections is the goal.

I think a flatter kite would give better VMG around the course, but there are limits due to measurement rules. Spis have been the area for most experimentation, but it is still the Gran Segel MK4 which is the choice. The sail John and Charlie use in the picture is a Performance cut. Interestingly enough, the reason the Gran mark 4 is the weapon of choice is that you can go quite high with it. Gran themselves say a slightly deeper and different cut will be faster VMG wise around the course if there are no other boats there. Contradicts my opening statement of course but that is part of the fun with sailing.

If the question is "do a flatter cut spi need less movement of the tip of the spi pole?" I would say the movement is so small already today that it dont make much of a difference.

That picture turned into an interesting discussion for us gearheads <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />