RE: Boomerang nano thrust line problem?
To check your engine thrust line you should trim for level flight at full throttle, then do a pass flat out and chop the throttle, if it dives you have to increase the amount the tailcone points down if it climbs up then you need to reduce it.
If your cg is correct and you have the tailcone of the turbine pointing down 3-5 deg and your control surface neutrals are correct then the only other thing it could be is tail incidence.