I am using 4s 2650mAh batts and getting 5 minute flights with plenty of WOT passes... my motor is the stock motor from the HK T45 64mm and the fan that comes with it is a 6 blade... I have cut it down to 3 blades and balanced it. My doppler passes average around 90mph straight and level.
Might try my 5 blade stock Stinger fan next and see how she goes... I have no doubt my 85A ESC will handle the extra amps... the batteries will probably need a vent to keep them cooler though!