Some time ago I've given up on providing explanations of what happens as I found out that these persistant myths are just that : "persistent".

Everybody putting in some time can look up the modern theories (although not all of them are, Arval Gentry did most of his work in the 50's and 60's) and educate him- or herself on the new insights.

But with respect to the kite, I'm willing to give you guys a hint.

Sure enough adding a spi will increase the pressure on the bows IF the remainder of the RIG is providing exactly the same drive as when sailing without a spi. And in most light to medium conditions we are sailing that way. That is the cherub example and also my personal experience as I sit further back in such conditions. However what happens when the wind picks up and a crew has to depower ? None of us depowers the spi, but depower the conventional "upwind" rig but making the mainsail flat or letting the traveller out. So in this situation, where the amount of maximum drive is limited by a FIXED dive resistance a larger portion of the drive is provided by the spi alone than say in light to medium wind conditions. How does this help calm down the boat ? Well that is easy. The spinnaker as a whole, by virtue of its inclined luff, lower centre of effort and other factors loads up the bows less per kg produced drive than the conventional "upwind" rig does. So when both setups produce the same drive; the conventional rig loads up the bows more than the rig with the spi. And that is what you feel. If you would power up the main fully again you would go both faster and pitchpole more violantly but because you are transferring drive from the mainsail to the kite, which is less bow pressing per kg drive, you calm the boat down while keeping up speed. Or if you really want to you can end up at the same controllability and higher speeds.

An important side effect in my opinion is the fact that a small amount of lee helm under spinnaker is very pleasent as it helps bearing away quickly when needed. Most conventional rigs however have an increased weatherhelm when broad reaching that is working again bearing away comfortably. This aggrevates the troubles when you encounter them. The spi therefor seems to pull the boat out of trouble once you encounter them while a conventional rig pushes you only in deeper.

I hope this helps

Wouter