My father learned acro in a Citabria. Years ago he got a ride in a C337 from a guy who flew them in Nam. He said they were boring along at 160kt and the guy asked what he thought about a split S at that speed. Dad said it sounded like a bad idea. Rolled upside down, props to low pitch, power back, and did the whole split S with the needle about stuck at 160. Lots of drag. My dad thought it was neat.
Bryan