Thanks for the replies. The reason I asked was that Ulman told me they put them on their spinnaker. They said the sails are so flat they are helpful.
Another question…
I have read wouter say that he would rather capsize than blow the spinnaker many times. Why is this? We got in a debate on the water about it and ended up testing it by flying a hull pretty high and releasing the sheet. The boat calmed down.
I think Wouter was talking about the mainsheet - not the spinnaker sheet.
The latest Landenburger spinnakers are pretty flat and really fly well at all sorts of angles - I think it's made the sail easier to fly without collapsing but made it more difficult to find and maintain perfect trim. That's probably what the tell tale trend is about. Someone crewing for me recently told me "geesh this thing is easy to fly without folding" and I got concerned about proper trim. Without seeing the leading edge of the kite though, it felt like it was drawing just fine...I may have to try some tales to see...