Leaderboard

I agree with @frob - Mystic 10 in an ST won't make a huge difference, and catching or playing with the flex is a game unto itself. With the UL, we switched to a dyneema bridle to lighten and shift the weight loading during glides, Mystic 10, less reinforcements (not needed on a UL), some other changes, roughly a 1oz reduction in weight. Overall, the UL is about some lightening, less drag from the bridle and use of the more flexible frame to more easily cup in lower winds.

I bought a set of Mystic 10 for exactly that reason. It doesn't make much difference in low wind conditions. You can fly with the 12's, including using a bit of oomph on a standard sail with 12's for flying indoors. The big thing I noticed is the 10's are more bendy. It isn't good or bad, just different. On the one hand it makes flight more squishy as it absorbs the initial strike to the line. This means you'll get a gradual buildup rather than a quick start since the initial energy is absorbed in the bend. It also gives the kite a bent look in stronger winds while your neighbor's kite will be more straight. They have a faster recoil that is more difficult to leverage with multiple fast actions. On the other, it enables a kind of one-two punch if you leverage the recoil. You get a delayed initial action then a surge on the recoil, and you can time your own second input to coincide with the recoil. While it does give a slower start, a double-tap or triple-tap with the recoil can act like a turbo button. Pop-pop-pop with great timing can get you moving rapidly in any direction even in dead air if you strike on the recoil. However, if you miss the recoil the energy will be absorbed and ignored.