I've now had an occasion to take a passenger twice since I started this thread. I went ahead and modified when I shift, as suggested. I shifted north of 4000 RPM, and did my best to match the gear to road speed to give me close to 4500 RPM cruising around.
For certain, the ST was a different animal at this RPM. The machine had all the power it needed to pull when I demanded it. And, the engine didn't make any pinging or knocking sounds the whole time.
In that way, the "problem" is resolved. That said, the ST is not silky smooth when running at this higher RPM range. I could feel a high frequency vibration in my foot pegs that isn't there at the lower RPMs I was driving in before.
The vibration in the foot pegs isn't a big deal. You may say "that's just what a motorcycle engine does!" I wouldn't have minded if the engine simply purred at this speed, but it is what it is. Incidentally, it is the sound and vibration cues that are given at this RPM that caused me to shift earlier in the first place. That and, the ST manual says to shift much earlier than what has been recommended here. Since so many of us treasure the owners manual and take it at its word, it's surprising to find this particular divergent view. But again, it is what it is, right?
Should I be expecting silky smooth over the entire operating range, or is it normal for the vibration to be much more pronounced in the 4-6k range?
Joel