You might also check the wing incidence. Relative to the stab, it shouldn't be more than a "couple of degrees" positive.

I assume that you have to use the excessive down-trim for a cruising throttle.

A couple of degrees of engine down-thrust would be adequate for this plane.

And check the balance. Tail-heavy may require down-trim to lift the tail, in addition to making the flight a tad squirrely.