I am currently running the 7XL with the 9920 with 16 GP3300 cells in my savage. The gearing is 12/51. The motor and esc gets under the hand warm tempeture. So it rusn really cool. I can gear higher if I want. With the 12 pinion I can get a really nice speed and runtimes are 10/15 minutes.
Here is an video of the BL J-savage :cool:
http://www.rcpics.net/media/Brushless_J-savage.wmv