http://142.26.194.131/aerodynamics1/...g_envelope.htm
He might have been concerned that there was no latitude for load shifting/people sitting too far back. He might have been aware of a recent incident involving this type going into an uncontrollable climb? Load shifting is always a possibility, and if the cg is aft, it might be enough to compromise safety or produce unpleasant handling characteristics. Personal preference- he's the one that flies it, not you! You might say that he should have warned you, but he might answer that he had every right to expect that you would load towards the ideal region more towards the forward limit. Why balance on a knife edge unnecessarily?