One point--somewhere in the deep (ok, shallow) recesses of my memory, I was told that an airframe is under its greatest dynamic pressure (q) in the low to mid-twenties. The indicated is around 280KIAS to 330 KIAS, the cabin differential is approaching it maximum and the air is "thick" enough to produce serious turbulence, if present. All this adds up to maximum stress. I don't know the engineering behind this, but it makes sense and tracks the history of in-flight breakups due to complete airframe failure absent convective turbulence and loss of control.
GF