Do you think he knew it would work? - had he practiced it before? Do you know?
My guess, having never met him? I don't think he had practiced it beforehand, but he had a lot of experience, in small planes and multiengine. My guess is he thought about it, probably quite a bit, and figured out what the indicators would be if the plane began to complain about being forced into a flight condition beyond what physics would allow. He watched for that condition, ready to back off if it came along, and when it didn't, he pushed the big new bird to the limits to which it had been designed, and maybe a fudge more. I doubt he even crossed his fingers. He had about as good an idea of what he was doing as anyone in that position ever can have.
-archy-/-