There is no use to tweak this Spitfire distinctive feature. The normal trim you can see as you start the plane in the air.
One tick nose up indicated, stick centered, elevator LE up a bit.
Trim the plane in normal way for take off, flight , landing , etc, only for zero hinge force or any force you prefer. And, for sure, no curves fo FF device for pitch. If you find this control too sensitive, just add a linear ~ 50% saturation.