According to Hitec, the HS-55 draws around 150 MAh when running. With 4 running that would be 600 mah. Add the power needed for the receiver and the ESC itself and you could be over the budget.

Note also that the load a BEC can handle also determined by the voltage of the motor pack. I have the Multiplex 27 amp brushless ESC with a 1.5 amp BEC. This is running with a 2 cell Lipo. Really climbs nicely.

Assuming you are using a 3 cell lipo or 8 cell Nickel, I would expect you would need at least a 1.5 amp BEC and 2 amp would be better. You might want to consider a different ESC. Sounds like that one is intended for 3 channel parkflyers.

Also, make sure you open up the air vent holes on the fuselage under the wings. They are molded in but are not open. YOu have to open them up or you cook the contents.