Brendan, The RS300 IS the "standard" size JR Synth receiver. It definately showed improvement when the batt was plugged into the Aux channel. (See previous post)

The RS310 is the newer/smaller version of the same RX but I have heard JR was able to miniturize it because they left out the BEC circuitry on that model. (not sure if this is a fact)

Thanks for your help.

The Grinch