oly 9

I hope someone smarter than me can help figure this problem. I have a 650 and an 850 transmitter. I tried to set up a glow plane with a throttle cut to kill the engine. I can do it with the 650 by adjusting my linkage and using the servo end points to fine tune the idle and wot. When I go to the throttle cut screen I can program the numbers to complete close the throttle to kill it with a switch. I cannot get the 850 to do the same. After rebinding the working setup to the 850 and programing the throttle kill it just makes the servo twitch when the switch is applied. I have the throttle kill screen the same on both. I have disconnected the throttle and played with the servo by adjusting the end points to the high side and to the low side.to see if there was any difference. Could it be that I need more servo travel range the gap between wot and idle? Like I said I can use the same programing on the 650 to work but not the 850.Anybody help??