Here's an alternative construction method using aluminium, epoxy and countersunk pop rivets.
It needs an angle grinder with those 1 mm cut off wheels, a good vice and hole saw and drill.
This is apparently how they build many aircraft wings so it should be ok.
I have used it for nearly a year.
The vertical tubes have timber dowling to add strength.
They also protrude slightly out of the scupper holes underneath so they don't go through the wall.
I simply tie it down using the existing black cleats.
The frame at the back is for a fuel container and the box holds spare plug and spanner.
I drilled 2" holes in the 1/4" aluminium face plate that you can see.
So even if the clamps come loose the motor stays on.
I also use a chicken strap to the Hobie handle just in case.
I run a 2 stroke 3 Hp motor which is difficult to flush.
May end up changing to the air cooled Honda.
Apart from emergency steering it is great for long distances up narrow creeks.
We have Finnis Creek at the lower Murray Lakes where it takes about 3 hours to navigate.
The reeds are about 6' high on either side, a bit Afircan Queen movie like.
Classic old B&W movie with Humphry Bogart and Kathryn Hepburn.
But I digress.
The best part, at the end of the Finnis Creek is a phone to local winery.
They will come and pick you up and take you to the winery for lunch.
So the motor is a great alternative for the return trip after a few wines.
The engine mount survived a capsize by the way.
I had to strip the motor and rebuild it.
The motors don't seem to like being under salt water for a while.
It seems ok again after the rebuild.
Cheers, Brian in South Australia