from the man himself-
And then asking about the spark plug as a follow up -the Flare model became the Kai-Zen twin after a few adjustments. the Flare would work well as a twin too... just a bit more curve and a couple other small tweaks.
the spark plug, compared to the flare and GX, has a lower tail rocker. the nose is about the same as the flare. the outline is a bit 'straighter' from the wind to just ahead of the fin. also in the fin area the deck contour is a bit 'flatter' and pinched toward the rail apex to let it dig in easier and hold more. the bottom contours are more subtle and the rail apex and tuck are a bit tighter. it's a pretty different animal than the flare and gX.