2010 FLHTP- Snake walk wobble 80+

2010 FLHTP 17k miles with rear Kumho Ecsta 195/55-16. Aside from conditional "square wheel" feeling the CT does well with the exception being a snake wobble at speeds around 80+. This is a prominant yet variable condition that seems to be more prevelant depending on (1) road surface (2) temperature (3) wind or not and maybe other conditions not as yet noted. I do not run a tourpak as suggested being "the" problem by someone else. I've tried pressures from 30-to 50 psi. It does seem to be less of an issue when riding two-up but I can not say this for certain. I did notice when I mounted CT on wheel that the Kumho sidewall is considerably more flexible than the Dunlop MT it replaced.
Could problem be something as simple as sidewall flex on this particular tire brand caused with some sort of centrifugal like force either lacking or exerted at those speeds? Do people with run flat tires have this same problem or not due to thicker sidewalls? I feel it has to be something simple and is most certainly not caused by an issue with my motorcycle. Any relevant thoughts & experiences would be appreciated. thanks in advance.

There are two Ecstas, the tire several Goldwing darksiders are using is the run flat Ecsta SPT,
and none has mentioned a 80mph wobble.
Are you using the Ecsta 4X, the all season non- run flat tire? How is it balanced?
The high speed wobbles I have heard about are usually related to some sort of flexing in the rear suspension or
a defect in the tire like being out of round or laterally imbalanced.
I'd be very surprised if it was sidewall flex that is behind what you are feeling.