I'm still thinking Jarno
"...In order for Jarno to ride his "hang-off" style, he lowered the clip-ons (handle bars) and excessively angled them downwards. Initially he got this from his previous experience as an Ice Racer in Finland before he started road racing. After Jarno's death, Kenny Roberts adopted this style and perfected it for road racing...."
Taken from here:
https://ccrma.stanford.edu/~peer/racer-jarno.htmlApparently Kenny gives credit in his long out of print book: "Techniques of Motor Cycle Road Racing". He states (here say, I have not read it) that Kel Carruthers introduced Kenny to the Fin style of body technique.