setup for crt.5???

[RUSTED]

well i want the crt.5 to go about 40+ mph but have about 15+ min of runtime, right now with my setup the crt.5 goes about 30moh and gets really hot and i get 8 min of runtime with a 2s 4000 mah , now i cant use regular lipo packs that are made for rc cars because i moved the motor forward (now the motor is on the opposite side of the servo) , now i need o know what setup should i go with right now i think i m8 go with the medusa 36-50-1600kv but i dont know whether to run 2 small 4s lipos in parallel or 2 small 2s lipos in series ???