[skeptoid]

Assuming 10 across seating that would require a gain of five inches. Looking at the detailed tech pages at boeing.com, it's not evident where that could be gained without designing a new fuselage. The fuselage 'wall thickness' is only about 7 1/2 inches which looks pretty delicate for a 21' 4 inch wide fuselage that's going to pressurized for many tens of thousands of cycles. Dropping back to 9 across takes care of the 1/2 inch and more, but you lose 25 to 40-some or more seats.

We big-boned individuals are not going pay extra unless we get wider seats. So the answer is .... different widths of seats for different prices.

Or they could weigh each passenger with his luggage and charge by the pound.

.....or maybe not ...

[Paleo Conservative]

The fuselage 'wall thickness' is only about 7 1/2 inches which looks pretty delicate for a 21' 4 inch wide fuselage that's going to pressurized for many tens of thousands of cycles. Dropping back to 9 across takes care of the 1/2 inch and more, but you lose 25 to 40-some or more seats.

Considering there are two walls, thats a decrease of 2.5 inches from each wall from the interior fittings not the external fuselage dimensions. If Airbus could shave off a couple of inches per wall from their existing A330/A340 cabin to widen their seats from 18.0 to 18.5 inches, I don't see why Boeing couldn't do something similar with the 747. It should work even better on a 747, because the wall doesn't curve inward as severely as the A330. The main reason for the decrease in wall thickness in the original A350 offering was new insulation materials that are thinner than the currently used insulation.