Does tire pressure drastically affect crosswind stability?

Words of clarification:

Those who recommend maximum PSI on the sidewall may (HOPEFULLY AREN'T) be correct.

They are correct (and only correct in this instance) IF, repeat IF you are at the maximum carrying capacity of the tire.

Stated another way, your chassis/coach maker made the TIRES the WEAK LINK to save money. I would read that as not a good thing. And if I considered a coach with that issue, would research upgrading tire size/load range so that I had a comfortable RESERVE on tire capacity.