Chris,
The ARF manufacturers (trainers in general) are pretty good at keeping things light in the tail so that a beginner does not have to work to hard at balancing. They use techniques like lightening holes in the tail surfaces or square stick construction. Not knowing the construction of the LT-40 I would'nt know what went wrong. However, here are a couple of things you might try. Is the battery under the tank? If not that can add a couple of ounces to the nose. You could also move your servos as far forward as possible. One of those heavy prop hubs are real good at helping a plane balance. A more extreme fix might be to cut some lightening holes in the stab, fin, rudder, elevator and even the fues. sides at the tail. Be careful as to much wood removal can weaken things. Hope some of these things help.
Tom