The critical dimension for that purpose is not actually weight, it's the width of the body, in a sitting posture, at any level (ie hip, shoulders etc must all fit in the space). It's a very easy dimension to define and check, and of course the maximum allowed is the width between the armrests (inside dimension) of the seat the passenger wishes to buy.
In that case I would suggest that the vast majority of the male population would have to buy two seats.
Do the maths for a 16" wide seat and you will be amazed at what the max chest size would be.