About lifting the bows. How much more "upforce" will the new profile of the sail produce if you let out 20-30 cm of the halyard? (Wouter is going to love this) Well, the short answer is 'not much' as the change in the resultant vector is not very large compared to the forces on the mainsail pushing the bow down. I have not done the math (I dont have that kind of math) but the reports I have found on the topic suggests this.
What I think happens is that the sail flattens when you let out the halyard and it rotates to leeward, thus it generates less power but also less drag.
If it was me going downwind, I would have set the spi with a tighter luff and sheeted the main in more. Then pushed the crew out on trapeze so we could heat up the boat. This from somebody with zero practical F16 sailing experience <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Do the I17s usually go downwind with the skipper sitting on the hull? I really look forward to start working on my trapeezing skill while sailing under spi!