proa rigs

Yes, it would be interesting. I think a twin-rotor Proa would offer some interesting options for changing balance and manoeuvring. Also, with the rotors turning in opposite directions at 'minimum drag' speed the craft would be in an extremely stable 'hove-to' state.

 

Hove to under rotor

According to Flettner, the rotors can be spun at a similar surface rate to the wind velocity and they "dissapere to the wind" this was his method of heaving to in extreme weather. Counter rotation of two rotors would equal out the lift forced ( ie one off the bow and the other of the stern for need of better terms in the proa vocabulary ) but both would still have high drag components which would also be in the same direction. You must expect these to be in the order of a coefficient of drag 3 -3.5 which will in effect drive the boat sideways at a very uncomfortable rate.
even reducing the rev rate will do a lot to keep things under control and that controlling device could be as simple as a thumb control on the tiller

 

What happened to the OP's original question about traditional proa rigs? Are you still looking?

 

The original question was about Proa rigs in general rather than traditional?

I think the biggest factor on what rigs can be accomodated is how much control there is over the centre of lateral resistance of the hull and outrigger - classic proa dilemmas of how to handle appendages and how much power there is in the rudder.

I suspect that many designs are tripped up by failing to anticipate that the CLR may shift forward as speed through the water increases.