Actually I'm going to continue with my new spi (sorry for the thread hijack). I got it out of the bag and compared its luff length to my old Ullmann. The GP spi luff is longer, as expected, but not as much as I thought, 17cms to be exact. I *think* my hobie spi has a longer luff actually (can't know for sure, it's on the boat)

So I'm fairly sure that my 2.9m spi pole is long enough to accommodate this new spi. But all the new boats have a 3.5m long pole, right to the class limit. What's the dynamic advantage in pushing the tack point that much forward? Lowering the center of effort? Lifting the front more? Opening the gap with the main? Or is it just a matter of "mine is longer than yours!"?