Dudley, don't misunderstand me.
Hoover (an a limited number of others) are special circumstances.
Everything I have read stated that the Shrike was a stock airplane.
I don't recall that Hoover ever spins in the airplane.
The video of the roll while pouring a glass of water is sure a hoot, though!
As I said in my post, in the right hands, some maneuvers not approve by
the manufacturer can in fact be performed safely.