Rollie Free and tank-slappers
Bear in mind this started because of the assertion that Vincents in standard trim were too dangerous to ride, and that Rollie Free himself might have been a factor in avoiding wobbles, on his dangerous Vincent, at 150 mph. I disagree with both assertions. Here's why.
I'm second to none in my admiration of Rollie Free, but the stability didn't come from his "skill and judgement" but from the steering geometry of the bike he was riding: Lightning "chassis" modification amounted to fitting rear-set footrests to a standard Rapide/Shadow/Comet frame.
I've experienced four "speed wobbles" (none on Vincents), three of which were all-out tank slappers. I can do no better than quote a friend: "Anyone who thinks he might control a tank-slapper has never had one. He'll have about as much control as a rat does in the mouth of a terrier." That describes exactly my experience.