I'm not sure that I agree with your "anything over 50mgs is an overdose" statement.

Modern vaporization techniques can bring the "smoking" dose range closer to the intravenous dose range, however I don't think this means you are overdosing by venturing above 50mgs.

Most dose ranges are calculated by body weight, on a milligrams to kilograms basis.

You also must remember that every individual has their own unique biochemistry, and that the quantity if tour 5HT2a/c receptors is determined by genetics.

Sleep, diet, stress levels, emotional state, set, setting, and drug combinations also play a role here...

-eg