A tank slapper and a speed wobble are two different things, Grouch. I have had both and they are scary in their own right.
The first was a speed wobble riding my mates H***a CBX1000 on the A78 Irvine bypass. I hit an indicated 130mph and the bars/bike started to weave then wobble. I nudged off the throttle and it settled down to about 80 for the rest of the trip. When I gave the bike back to my mate he says "just accelerate through it and it'll go away" I wasn't that brave
The tank slapper was on my Bonnie doing about 35-40. It was a stretch of road being repaired so the top layer of tarmac was scraped off. I hit the corner of a raised manhole cover (it was back in the day, so "manhole" was an acceptable term ), anyway the next minute I'm being bounced all over the road with the bars slapping back and forth at an alarming rate. I managed to slow and stop, and once off the bike my arms were bloody aching and stayed sore for a couple of hours.
Another time on my xs1100 I arrived at work and my mate who had been following in asks about the weave of the bike. I told him I dont notice it anymore and its just part of owning a 1970s Jap "Superbike" with an elastic frame.... My good lady organised the sale of that bike one day a delivery guy showed up with summit. He see the bike and starts asking her if its for sale. Yes she says, he showed up later that night and bought it.