About double trapping downwind on the T. You got to find the best VMG, and for pure downwind sailing in the big stuff it is with one on the wire and one on the tramp (or hull). In a distance race however, the angles and VMG might be best with the kite up and two on the wire. The T kite is so flat that you can build some really serious apparant wind. Boat feels like it is skipping over waves, but you are balancing on a thin edge. A sudden lull is enough to capsize the boat over yourself. Quite fun to look on when a crew pulls the boat over themself..
Having just the crew on the wire also make it easier/faster to manouver, which might just be the thing in a large regatta.


These guys seem to think double trapping under spi is fast <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

(but the mainsail looks a bit flat in the top. Perhaps their downhaul is maxed <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> )

I would not bring windsurfers into this downhaul discussion. Their requirements are a bit different than for catamarans and they have some quite specialized sails and masts for course racing, wave etc.