10 years later...  Try this:

rated_N2_rpm=12250

You will definitely no longer see rocket ship performance.  I loaded up to max TOW in ABQ in 20 degree C and it was a real struggle to get through the flap retraction.  Keeping thrust at mac continuous, the best she could do at 270 knots was 2K.  Bu the time I got to 2000, 1K was about it.

For the first time ever, my jet is actually UNDER powered.

I got the number here:en.wikipedia.org/wiki/Pratt_%26_Whitney_JT8D