Don't mess with the flying surfaces trim -- your Nexstar has too much right-thrust. This is a Nexstar QA fault that seems to affect a small nunmber of them to varying degrees-- some are so bad as to be uncontrollable. The fix is to reduce the right thrust. It can be done by removing the engine mount & fitting a wooden wedge to the face of the firewall (hard balsa will work -- just toughen & seal it with thin CA). Another fix is to remove the right-side engine mount screws & fit thin flat-washers between the mount & the firewall, then replace the screws -- this one has the advantage of not having to remove the engine & mount. The disadvantage of the flat-washer fix is that it concentrates the impact loads in a hard landing (crash?) & can accelerate firewall failure.