effect of changed thrust line.

OK - got some more info.

The center of mass is something like 34 inches behind the firewall
and roughly 7 inches above the top engine mount point on the firewall.
so roughly speeking 13 inches above the prop centerline.
The prop flange with the O200 is 29.75 inches from the firewall.
This means it is 63.75 inches from the prop flange to the CM.(center
of mass)

This means there is NO WAY the thrust line is aligned anywhere close
to the center of mass.
This would require a downward displacement of almost 15 degrees.

THAT is not going to fly - PERIOD. We are hitting about 5.5 inches
BELOW the center of mass

If we aim for the middle of the rear stabilizer, about 183 inches from
the prop flange, 1.5 degrees down is 5.5 inches above the prop center,
which is about the middle of the rear of the fuselage and roughly 10
inches below the center of the rear horizontal stabilizer .

If I want to hit the same spot with the engine down 1.5 inches, i need
to change the angle to 1.875 degrees.
2 inches goes to 2 degrees.
2.5 inches would be 2.15 degrees, +/-
3 inches would be 2.31 degrees
4 inches would be 2.58 degrees.

Does this make any sense??
It sounds right to me.