Rather than adding ballast in the form of a NiCD or NiMH pack, I recommend disconnecting the power lead from your ESC to your receiver, and using some form of separate BEC. I'm partial to the ParkBEC myself on any aircraft where the total servo draw is lower than 1.25A and the voltage is less than 30V:
http://www.dimensionengineering.com/ParkBEC.htm

Using some form of separate-from-the-ESC BEC will deliver a substantial weight savings over running a separate Rx pack. However, if you're looking for something that can push more amps from your pack, you'll want a bigger one than the ParkBEC. I have some friends who have this one for .60-.90-sized aircraft and swear by it:
http://www.koolflightsystems.com/ultimatebec.htm

The Kool Flight Systems Ultimate BEC is good for up to 45 volts. If your power system uses more than 45 volts, then you are back to the old standby of "strap on a receiver battery pack". But considering that 45 volts is the equivalent of a 12S LiPo pack, you'd have to be running something seriously beefy, and probably want to have dual receivers and dual packs for a plane that expensive anyway

Regarding the "2 servo rule", it's important to remember that those ESCs are usually referring to STANDARD-size servos. There's a world of difference in amp draw between, say, a Hitec HS-55 (sub-micro) and an HS-311 (standard economy) servo. The draw will be higher in-flight due to pressure on control surfaces, but if you fully-deflect all your surfaces and measure the draw from your battery pack with the motor off, what's your draw? Compare this to the draw on standard servos, if you have any in your shop.

It's helpful to measure ESC temperature after a flight, too.