KeithB - hats off to you on a great motor design. I did a lot of research and decided to go with your approach as I didn't like how the cheetah mount is so low to the water, etc. However, I decided to build-off your design and, at least I think, I've come up with "Version 2.0" that takes up the functionality a few notches as well as improves the structural strength. Here are the main improvements:
1) I couldn't get over the piece that sticks into the cross bar. The torsional force on this load is high given the short distance from the fulcrum point (i'm not a physics expert but I intuitively sensed this) And since we have to drill the cross bar anyway, I put through bolts all the way and used a stacked sandwich of plates to get the spacing right.
2) I also specifically designed mine to minimize the length of the extension bar to also reduce torsional (rotational) force on the cross bar.
3) I am using the Torqeedo motor which hangs down a lot even when in the up mode. I liked the fact that the cheetah mount raised up as I often take out several adults and so the hulls are loaded down in the water. I didn't want the motor splashing and draggging, so I designed a hinge mechanism to raise the motor up.
BTW, I like the torqeedo as i mount just the motor and have a battery extension cable to keep both the tiller and the battery on the boat (further reducing weight from the motor mount and the forces on the cross bar).
I have more pictures and details I can post if people want it. Here's the setup (if this link works - this is my first post to any sort of message board ever):
Robert
https://drive.google.com/open?id=17Qzc_KVCyGiNjd5JdB7Ij7eUp4_xEMhW