Dont ever try to handle the plane with the engine running and ANYTHING else at the same time. Just sit the radio down and carry the plane out to the runway. Then go back get your transmitter and go fly. A lot of people frown on walking away from your Tx, but seriously if the connection os lost between the Tx and Rx what good is having it in your hand? Best thing to do is have some one else set the plane out for you.

I LOVE Kens idea for a throttle lock but I still say you are crazy to handle anything else when you have a plane in hand.