I'm curious to know from LBboarder what rigs are being used with the new longboards; is it mostly 10m rigs with lots of draft and adjustments, or are people actually still using little 7.5m rigs?
Somewhere on that site, it says something about lack of deep draft rigs for longboards....all I can say is check out the glide from severne; that sail has grunt like you would not believe; it feels (in power) like a 10m but is significantly smaller than that.
I don't really follow longboarding that much; but AFAIK the Phantom was pretty competitive at a world level with the right guy sailing it. I've tried not many longboards (Kona, IMCO, Mahola, Phantom 380, 320, some other old one) and the Phantom definitely (to me) felt very very nice and planed up surprisingly early; if there was any where to race one here I'd even consider buying one; good fun.
As for kites; given the windsurf hot angles downwind scenario option and the difficulties of supporting a kite without a backstay, I'd suggest just run more area and sail windward leewards or learn to control a big rig on a reach.....would be cool to see though ;-)
The whole philosophy of sportboats like a M24 is to suffer upwind and then make it all back downwind and so you just need to paste them upwind is the best idea :-) The M24 is going to really struggle (like most sporties) in about 6-12 knots, when the apparent requires sailing angles but you can't plane to make up the extra distance..... the M24 is miles slower than a tornado or a 49er as it only does 6.7 knots (at a guess) upwind; and even for a spotrboat it is fairly mild by today's standards; this is my idea of a more extreme sportboat:
interesting to learn the prodigy is dying; doesn't surprise me; at the end of the day a lot of those boards are being superceded by newer models; Kona presumably has stuck it to the prodigy - C249 is this what your numbers suggest?