Tricopter tail-rotor

Trying a tail rotor (vertical blade on a forth motor) instead of a servo for tricopter back end.

The servo wears out too fast; way too much action for the little guy.
A traditional helicopter tail rotor counteracting a slightly tilted back motor seems like a better design.

The big problem is that in the unarmed state, output pin-7, designed to drive the servo, takes the mddle (1.5ms) ESC value. This causes the tail rotar to rotate at half speed.

The three servo parameters don’t seem to work. Not sure they are the answer even if they did work.

Anyone with some knowledge of the firmware?