A 600 Mah pack will not last a very long time, especially with the Hitec 645MG servo. The higher torque servos will drain more juice from a battery pack. Your best bet, is to run for a little while with that pack, but keep an eye out for a good 1100 or 1200 Mah pack. This is the MINIMUM you should run, with 3 servos, one of which is a high torque. HPI has a good 1200 Mah pack.