I "think" what you're asking is that your generator head is solidly connected to a short section of 2" pipe that just sits on top of a 3/4" pole, yes?
If you are concerned about the head assembly lifting off in a gust, there are several ways I'm sure we can figure out to keep it on, while still allowing it to rotate freely.
One option that pops into my mind is to somehow attach a short section of 2" pipe to the existig head stub, but with threads on the lower edge. (you could even use 2-1/2" pipe slid over it with JB-weld epoxy)
Remove the head assembly, and slide on a second threaded pipe section that has a union on top of it (a union would be about 2-1/2 to 3" in diameter and has threads in its inside diameter). Firmly attach a hose clamp around the pole just below where the head assembly threads sit, then set the head assembly back on. Slide the pipe/union up and screw it onto the head assembly.
The head would still free to rotate, and the hose clamp inside the union air space prevents it from lifting off. If this would work, play with the parts at Home depot before buying. I might not understand your concern correctly, and even if I do, there's a dozen ways to skin this cat...
(disclaimer: no actual cats were harmed in the forming of this metaphor
