The Shadow IS very quick up wind in a blow.

It has a small mast section as the kite is small and has a short luff (so lesss stress on the mast).

It also appears to have a good "upwind" hull shape; it's a bit more of a challenge to sail down wind as there is a lot less volume up front than the Stealth / other F16's.

Classic comments when sailing at my club is that they might be first to the first windward mark in 15+ but if more (20+) I just slam the kite up around the windward mark and disappear in a cloud of spay and they "survive" down wind and may well leave the kite in the bag at times....