Nice props JMTW. Are they spring loaded in the bulb for forward thrust?
I am assuming that the servo does not act on the shaft unless you want to reverse thrust.
And that if you return the servo to forward thrust, the blades have to follow the shaft back somehow.
Wait if the shaft moves in and out of the propeller hub, why does the propeller not fall off..
Hmmm I'll have to think on that some more.

I have a pair of the [link=http://www.rcgroups.com/forums/showthread.php?t=77749]Voith Schneider drives[/link], and I don't think that the Kontio has the height in the stern to clear the motors and control connections. Harbor models sells them and they can be special orderd through Hobby Lobby International.