The Stealth does have a lot of rocker and a very flat bottomed hull design. I imagine that this form helps produce lift whilst also increasing the ability to go through tacks and gybes quickly. This coupled with the 'T' foils certainly helps drive the boat hard downwind, or as was the case at Zandvoort feel comparatively safe whilst going downwind. John and Paul Alani were twin wiring with kite on the runs with their Stealth at Zandvoort whilst Hans only occasionally hoisted his kite and therefore the curved traveller paid dividends. It is also worth while mentioning that Hans has only been sailing a F16 for 3 months previous to this he has been a very keen 'A' Class sailor. So even in his own words he is still learning to sail with a kite.
P.S Matt and Bart won every race in which they didn't go swimming.