Finding "Neutral" Position on Piper Elevator/Trim Tab

I have a '79 Piper Warrior with a floor-mounted flap lever/trim wheel
and cover. The trim wheel has a metal needle pointing to a sticker on
the cover to show "neutral". The only reason this matters is that
setting the trim wheel/tab to neutral is part of the pre-flight
checklist.

The plastic cover was old and cracked so I replaced it, carefully
noting where neutral was and (my mistake) re-used the old label.
Whatever glue was left on the sticker after 25 years quickly faded and
the sticker is now gone. I can replace it with a new one from a label
maker, but I can only estimate where neutral is. My local FBO/shop
says finding neutral is not simply the 1/2 point between full up and
full down. You need protractors, string, and an advanced degree in
Euclidean geometry.

I'm not worried that the plane will violently pitch up or nose down on
take-off, but it would be nice to set it properly. Any guidance on how
to find the neutral position?

Thanks!!

--Jeff