Nebbie is right; whether the model sits on it's tail or not isn't directly related to it's balance about the CG. I don't know this particular plane, but many times landing gear are bent such that they angle away from the wing in the fore-aft plane. If this is the case, it could be that your gear is installed backwards, and should be reversed so that the wheels sit farther to the rear. Otherwise, it could be as Nebbie says and the gear may need adjusting. In either case, for a trike gear plane the main wheels must be behind the CG.