Frames were changed from sheet metal to milled aluminum and reduced by 2" thickness each, giving a total of 4" additional space.
So they might be as strong as on the "traditional" 777 but more flexible (stiffness increases at the order of 4 with thickness), causing more deformation to the door surround structure and putting more loads on the locking system.
We will see.
At 787 times we would already had all the pictures circulating the web...