Lexan window cracks - help needed

in the process of repair Ive often found windows that survived surprisingly well for how poorly they were installed
catastrophic failure isnt that common its just far more likely to occur when the job is done poorly

 

I think a hidden factor is just how rigid (or flexible) the surrounding frame happens to be, or the Cte is close enough. Sometimes you just get lucky that way. Also, surface mounting is a big plus since the panel won't be 'trapped' all around by the frame. Through holes are still a problem, though.

I'm working on a plane right now where one piece of glazing was obviously mis-installed; not enough expansion room all around. But it's a 'clamped' rather than 'through-hole' installation so the whole window just caved in permanently, but no cracks anywhere.

Jimbo