H.P wrote:

Then his CG moves forward and he's nose-heavy and outside the limits
envelope.

Doubtful. What does a seat weigh? 15 lbs? One time I carried a 280
lb man in the front passenger seat of a C172SP. Despite having almost
a total of 500 lbs in the front seat station, the aircraft was still
within the envelope (less than full fuel, of course).

--
Peter