Interesting to note that the Sud Aviation Caravelle had triangular windows and the L1011 Tristar had square ones. I heard a while back that Redux was originally specified to secure the windows, but de H management were not convinced that this method alone was good enough to rely on, and insisted on the addition of rivet plates and rivets, and it was these additions that initiated the cracks.
I am not sure how true this is, but the record of the Cravelle and 1011 suggests that (within limits) the window's shape is arguably less important than its construction.