This might be a silly Q from a nitro guy:
But why don't you all wire those power hungry servos up like the 7.2V servos? just have 2 diodes inline on the positive lead on the servo to give a 1.2V drop from the 7.2V battery (or 3 or 4 diodes if your worried about too much voltage). That way the only thing your ESC BEC circuit is powering is the receiver. Maybe still install a cap but this could be much smaller. You should have no power problems then. Would give the servos a much better power supply - if its dropping in voltage to knock out the receiver your servo performance could be also suffering (maybe only very small amount).