Possible CG problem... roll it inverted. Does it now need a lot of trim the other way? If yes... its CG too far aft.

The power test... may or may not pin it down to thrustline... stay9ing upright, level and adding power adds airspeed so you can end up correcting an incidence problem with thrustline. (which is not good.)

www.nsrca.org has a complete trimming chart. follow the chart and it will tell you whats going on for sure.

Of course... note that the chart is designed for the full symetrical 0-0-0 pattern designs. The Eagle is not one of those designs... so the dive test may be flawed. If the plane has "decalage" it will pull up. If the wings are not symetrical... it will pull up.