So these actually DO improve handling?
The most honest answer has got to be yes, no and maybe. Some experienced no real change at all. Some experienced significant and immediate improvement. And some experienced smaller changes at various margins.
It really does seem to vary bike to bike, and rider to rider. Can remember a couple of the group having profound wobble/whatever that was nearly all initiated by airflow over the nose. One the front started the rear end tried to keep up.
Much of the shake in the Electra Glides is often air coming up underneath the inside of the fairing and giving it a shove. That shakes the bars right along with it of course.
For me the the Ride-Str8 thing helped one particular issue. On long sweepers taken at "moderate" speeds the ass end would often not want to straighten out as quickly as it should. Would even oversteer a bit at the end of a turn, or at the end of each turn if they were in succession. Enough that a correction had to be made. It was never bad (at least once you knew it was there). The new device in the rear made that go away.
That was the only ill behavior I ever had that started in the rear though. Everything else is just wind up inside the fairing. And that you just have to be prepared for.
The sta-bo bushings I got because I got them cheap. That's the only reason I tried them. Someone got them, didn't like them, and sold them for $35. For that it was worth it to experiment.
There was a difference with them. And one I liked. It wasn't great but it was beneficial. They "stiffened" the back end of the bike up when finishing any turn. The whole bike responds to throttle application to be pulled upright more quickly and "solidly" from from to rear with the bushings in compared to without.
Had no idea what to expect of them. So when noticed that right off the bat it was a pleasant surprise. As said, it's not a huge difference. But it is a good one.