why not purchase the 8000mah packs that kershaw sells?
Or, I would look into some of the 4S 7500mah VANT lipos and use those in series for 8S and adjust gearing accordingly.
http://thebarnfloor.com/catalog/prod...6#.VjjvYCvpw-4
with more voltage and proper Kv and gearing, you should see better running especially in temps.
Love to see some pics and more info on what you have.