I'm definitely a fan of the oceanvolt installations that I've seen and believe it could be a great option for a harryproa. Their ServoProp actively controls the pitch of the propeller blades which improves regeneration efficiency, prevents runaway damage at high sailing speeds, makes reversing much more efficient (possibly a fixed direction installation could be effective for motor sailing in both directions), and also gives the option of setting the blades neutral for minimal drag while sailing even with the prop always in the water.

The question becomes how do you mount a saildrive unit on a flat bottom proa without requiring beaching keels. Could you put the whole unit on a swinging leg mount on the beam? A sort of well under the lw hull? Leave it fixed and keep very large tires to protect it while beaching and a small skeg to protect it shallow waters?

Does anyone know how efficient the OV ServoProp regeneration is in reverse? I could imagine that regen in reverse may actually exceed regen in forward operation due to the prop curve being optimized for forward propulsion.