It looks like the the rear swingarm extends forward of the pivot and ends at the foot pegs out front. I suppose a feature would be variable rebound damping via his legs?
+1 for his use of triangulation in the frame design, although he took some artistic liberties.
He will have some unsprung mass, but his belt tension will remain constant during suspension travel if he mounts his motor on that forward-extended swingarm. If he doesn't like his foot pegs swinging he could just drop them down from the upper frame instead.
"A conclusion is the place where you got tired of thinking." -Steven Wright