Originally Posted by
DaveReidUK
Thinner insulation and redesigned sidewalls. Nothing structural.
The fuselage redesign was most definitely structural - they made the side wall structure 'thinner' to open up more interior space.
As Aihkio notes, I wonder if it is related to how the fuselage was being held down. When they did the ultimate load test on the 767 nearly 40 years ago, they never broke the wings because the fuselage broke first. They were already above the 150% load limit when the fuselage let loose so they didn't need to repeat the test.