the bottom line is this may be one of those times when more is better! If your idle is to slow,you risk damage,if it's to fast you risk higher oil pressure at idle (oh my!) and using a bit more gas at idle, gas is a bit cheaper than your top end!

I'm pretty sure these bikes were Just as Without a tachometer when they were introduced. I don't think GPS or cellphone metronomes or anything like that existed.

Use your God given Brains.
Read the advice.
The tag on the frame says 1100 rpm.
Everyone knows that Low rpm screws it up.
It's not rocket science.
If you can't ride it through a parking lot at idle in low gear because it's too fast for you, gee, maybe it's taching a tad high.