I first ran mine to 7k in 2nd gear after only about 300 miles, then backed off and let the engine compression brake. I repeated this a few times as the mileage increased, allowing a little more rpm each time. I probably didn't hit 9000 until the engine had 800+ miles on it. I preferred to gradually raise the imaginary redline over time rather than all at once.

 

I was at 599 coming back from a trip designed to add miles to the car. I was headed back to civilization and was at the last intersection before the "real world" of traffic and pedestrians started again. I decided, ok, good enough and went for it! 9000RPM in 1st 2nd and 3rd. Giggles for miles and grins for days!