here is my answer to point#3. may be relevant or not...
Sailing downwind in 27 knots on an 18-spi up, is prolly near the limit for even the really good teams. How smoothly the run goes would depend on how big the seas are, and how gusty it is . You would have to land the jump off the back of one wave to the wave in front every time that issue came up..
We have 27 knts regularly here and i have no spi on an old TheMightyHobie18. i use old school technique and just sail low with the crew playing the jib and me playing the main with the traveler set out where i like it for that particular run. You can get going pretty fast by surfing and there is a trick to steering over the wave in front. Speed is your freind. When you are sailing low in that wind the crew needs to sit on the ream beam near the middle of the boat quite often. It helps to have an strong agile crew that really knows what they are doing trim wise.