Les, I don't know how much this might help, but its worth verifying if it helps with the diagnosis. From what I understand with JR receivers in a low voltage condition, is that it will start 'clipping' under a high load condition, and not go into failsafe. Basically, my understanding is this. If a servo load pulls down the voltage, the receiver basically turns off when it reaches its threshold level. Once it turns off, the servo load ceases, and the voltage then rises above the threshold. Once it rises above the threshold, the receiver comes back on line and starts applying load on the servos as it would normally, and the process repeats itself. Thus, one would feel sluggishness in the controls, but it doesn't go into failsafe. With Futaba, the receiver has a battery failsafe which effects the throttle, but I am not sure what happens it if drops below the battery failsafe threshold, then further fast the receiver threshold.

I heard this description of the 'clipping' in the past, but never verified it with JR directly. It might be worth asking JR about it, as it would then possibly point you in other directions for resolution.

Regards,