Mr. Matthews makes some excellent points, but one which I'd like to emphasize is in the quote above. You are under no obligation to make your initial test flights with the "final CG". You can ballast the model a bit nose heavy at first for a greatly increased safety margin. You may pay a slight price in performance, but that's of no great consequence at first. The objective of the first flight is to get up and get down in one piece and learn something about how well the machine functions. You don't need stability or handling problems to complicate your task.

Once you become comfortable with all the other operational aspects of flying the model, you can evaluate the pitch stability and then begin to sneak the CG rearward in careful increments.

Dick