Max prop on a saildrive
Actually, in forward the MaxProp provides about 96% of the efficiency of a fixed prop. The difference in drag under sail between the Max and folders is virtually inconsequential. In reverse the MaxProp provides much higher directional stability and efficiency than any folding propeller and approximately 80% of what a fixed prop would provide. If maximizing performance under sail and preserving backing power is your concern, the MaxProp is probably your best choice.