Ordered a sample* because in my book when it comes to developing a prototype you can't argue with free.
When building cats https://www.boatdesign.net/gallery/6-flat-cat.30015/ prior to the monoski, which I pursue to paraphrase JFK not because it is easy but because it is difficult and because I'm that stupid, I used something like it to mount the motor.
In that case I glued the plate to the back of the motor and drove the shank into the airframe, which proved sufficient and especially so because the motor supported a 'pusher' propeller that drove it towards that airframe rather than a 'tractor' that would try to separate it.
Happily the centres of those holes are already set at 29mm, not far adrift from the 30mm bolt-holes used to mount the U7 motor. It appears a universe known for slinging mud my way is conspiring to get the mono-ski built?
* Does mean I'm signed up for a newsletter but am always keen to keep up-to-date with the latest furniture feet at weekends.