Diaphragm on Steep-Pitched Roof with Attic Space

[swooneyWOODSTRUCT]

See attachment. The red lines are showing where I have plywood diaphragms. How much of the roof wind/seismic loads should I take into the attic diaphragm?

 

[phamENG]

If the attic floor is sheathed in plywood with competent diaphragm fastening, chord details, and everything else, I'd put all of it there unless there's a compelling reason somewhere else in the load path to consider the roof diaphragm to be the more rigid option.