I'd say even if the power has dropped slightly past peak if it puts you in a higher point on the power curve by shifting later and losing a bit of power up top you are still picking up an advantage. This all depends on the amount of loss up top though.

Woudl have to agree 9,000 is a good stopping poiunt for stock parts and a dyno is needed to to know if that is useful. I rev my stock cams to 8800 and they plateau and then drop around 8000-8100. It is gradual so it is useful to rev past peak but not by much.