While sitting well above the ridge at SGU Portmoak in a K13 in the late 60's, I got the "suspended in the middle of a fishbowl effect. I felt like I was hovering in nothing but a void. It was quite scary until the feeling passed in a few seconds. I never experienced the problem while in the RAF, flying on ex in everything.
Later, I had the same experience in a Piper Arrow in the cruise in perfectly still air but I found I was able to rationalise it away by concentrating on the coaming and resisting the urge to look over the side.
Not long after, I became absolutely panic stricken leaving the ground in any kind of commercial aircraft at all. Becoming violently ill and with ferocious diarrhoea, the symptoms of which started up to a week before I had to fly. In those days I could usually wangle a trip to the flight deck where the fear of the aircraft breaking up almost immediately disappeared. It took several years for the fear to subside and now it has almost gone.
Severe turbulence no longer has me gripping the seat and needing to get to the head at the risk of bouncing of the ceiling.
IG