C-25 Fiberglass distorted between the window frames

Jul 7, 2019
16
Catalina 25 161 Drummondville, Qc, Canada
I'm repairing the windows with the CD kit ... in doing so I found that the balsa core has disappeared on the starboard side where a window had moved a little down, the port side is okay. I removed the inside of fiberglas around the windows to replace the core and noticed that the outside fiberglas between the windows made the "banana". the horizontal part of the middle goes inwards. The metal frame of the windows seem to me straight and not curved ...
it was getting late and darkness prevented me from comparing with the port side.
So I would like to confirm that if I put a metal / rigid rule vertically the fiberglas should be as straight as the rule... or the curvature is normal?