The rubber tubing I was referring to goes between the motor shaft and the prop shaft. There are no mechanical connections or grub screws involved at all as it's a tight fit onto the two shafts. When under drive, the rubber self tightens and produces a good grip.
I have seen your idea Brian but prefer the simple push tube. It will be used on the Schottle drives in my latest craft and not be subjected to undue forces or high revving.
The advantage of this system is that it allows for silent running and vibration free movement. The speeds are usually low, so extreme forces do not affect it. I have used 'sturdy' rubber from Mark's Model Boats in the past but felt it wasn't flexible or thin enough for this particular system.
Hope this helps,
ken
