From The "Wayback" Machine ...
If, for some reason, you have a "mature" avionics package (nee - sans electronic "marvels") you can wire the servo to two parallel circuits.
In cruise, you would like to slow down the servo speed so as not to "overshoot" trim tab movement each time you "blip" the switch.
In the pattern, you would like to have the trim "reaction" be as quick as the servo 's op speed.
In simpler terms - the faster you are going (cruise), the slower you would like the trim input reaction to be; and, the slower you are going (pattern/landing) the faster you would like to input reaction to be.
The circuit for "cruise" is wired through a speed controller, so that op speed can be controlled to your liking.
The circuit for "pattern/landing" is wired (at full speed) through a micro switch activated by the initiation of flap movement.
Two parallel circuits for a mechanical solution - simple, but (very) basic compared to the electronic options available to new builds now.
YMMV - but this has worked for me for more than 20 + years.
HFS
HRII S/N 002