I'm installing an Optic Kill switch but encountering a problem;

- Radio being used; Futaba 7C 2.4ghz

- using channel 5 to plug in Opti Kill switch (this channel used to be used for Flaperons)

- After instlling opti on the Ignition battery, the LED on the Opti switch comes on (indicating it's armed) Only when I apply Up elevator
- It comes on with up elevator even if Manual Ignition Kill switch is Off.

I'm obviously doing something wrong here as I know the LED is supposed to be on all the time indicating it's armed.
Is there something I must do with TX ie; channel 5 , it's the same effect either inhibited or with full ATV.

thanks in advance