It was some time ago, but in the meantime we've adjusted our boat (as suggested by you), and brought the spinnaker pole around 20 cm's down. Indeed the spi is a lot flatter, and yes we drive it deeper now, which means less agressive corrections. So once again: Thank you all for the help! Furthermore we've adjusted the mast rake a bit, and found out that the spreaders were not equal. So we corrected this.
Sunday we had some nice weather (16-20 knots) and made a short video:
https://www.youtube.com/watch?v=k4WLqQjgBZAI agree as you say that it still looks a little round, however I think this is also the video. We see (and experience) it's a lot flatter.
Still we have one last question. To keep everything in control, basically we drive our spinnaker most of the time sheeted in rather tight. (maximum sheet length between the boat and the spi is 1 meter) However we were more or less overtaken by another boat (very good sailors who were doing a racing track) who had the spi very "open" and more in front of the boat. It looked very fast and also in control. We tried to do the same, but as I tried it collapses every time. We have to keep it more or less in line with the jib.
Can anybody explain this? We still have to learn a lot about spinnaker sailing especially at 16 knots and up.
