IMO you need to set it for minimum or to kill the engine. Jets are REQUIRED to kill the engine upon signal loss. If you can't control it you MUST assume the worst (battery or switch or RX failure) and that you will NOT regain control. Therefore you want the plane to come down ASAP but with the controls at a neutral position. Any control that is input will be there until the crash. Please note that some failures, like loss of battery or switch, will not allow failsafe to work because power is required. So you want to hope it is just a signal loss.