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For clarification; my comment was directed at not killing myself. I could give two sh*ts about regulatory compliance. You are correct though about it being SOP back in the day. My dad flew B24s (15th AF, Italy) in the Big One and they practiced spinning in the early part of their training, no big deal (BT-13s, PT-19s). I just recently (1981) got my Private Pilot rating and there was no spin training required as of then. It wasn't until I became a CFI in '89 that an examiner showed me how to do it. It was fun/I enjoyed doing them in a Cessna.
A closer analogy would be if somebody handed me the keys to Miss Budweiser or any other Unlimited Hydroplane, I'm fairly certain that I would not push the throttle all the way to the stop on my first trip down the main straightaway. I'd probably ease up to wide open power after a few laps, just sayin. YMMV