I just spoke this evening to an English couple on a Roberts 38 called "Serenity" who've been out cruising for years and are now doing the Great Lakes after...Brazil...
Anyway, they have an Ampair wind gen, and they commented that they make their real power (6-10 amps) towing the thing behind the boat on downwind runs. As they sensibly pointed out, the wind genny barely moves on a run, so you might as well tow a generator.
http://www.boost-energy.com/ampair/p...s_product4.asp