I had a RTF Nextstar I had gotten for my wife and daughter to learn on. It flew great with added weight to the nose the AFS disconnected and the speed brake flaps still in the box. Went down to the field to show them how it flew, smased it into the ground at the end of a loop. Got a ARF one to put all the gear in, spent a few weekends trying to get it to trim nothing we did worked. Checked the AOI was +5 deg. is speced at -2 deg. check the incidence bet you will find it or the engine thrust is way off. I can't tell youif this will fix it as I just found this out today, I have yet to shim the wing and fly it.
Ther ARF (Select) was a nice plane the ARF well lets just say it is not select.
If it doesn.t work I will get them a Sig LT 40 I know they fly good....
Oh yea RE the right thrust first plane I have ever had to use left rudder on takeoff.....
Good Luck

Check out "airplane will not trim" in aerodynamics.....