This is good advice. I think you'll find that the faster you can execute the shift, the smoother and quieter it will be and the less stress it will put on the transmission. I also think you'll find that if you shift at a lower rpm, the shifts will be clunkier and worse than if you shift at a slightly higher RPM. The higher the RPM, the less load that is on the gears, which makes them engage smoother.I have found that if there's any delay in the shifting, it gets "clunky". In other words, when you want to shift, don't preload the lever or hesitate in shifting at all.... pull in the clutch at the exact time you move the shifter. Let out the clutch momentarily at half way and then all the way out. This allows the gears to mesh up and transfer the power to the wheel without jerkiness or noise. Takes practice but my shifting is generally just a slight click being heard. Don't hesitate and you should have smooth shifting.