I was about to reply to you last post but I see that you have discovered the fault in your own line of thinking.

Indeed, an important parameter is how far the luff of the spi is in front of the mast. By ruling on a max pole length this measurement is always the same and so too performance. The same measurement together with the gate high measurement (also a fixed length) fixed the luff length of the spi which is the only other important parameter of spi performance. Therefor these two rules are very effective in forcing all spinnakers to the same performance. That is unless a builder decides to use a shorter pole then allowed by the class rules. But that is a private decision.

I'm also very happy that we have done away with that complex pole length rule that F18 rules and Texel/ISAF use. That was both a performance equalizing nightmere as well as impossible to explain to most owners/builders.

Wouter