From what I understand, the solid plexiglass sliding hatch covers warped by the heat generated from the sun beating down on them. Catalina changed the design of the sliding hatches which now are made of fiberglass, with a plexiglass insert. I think this change happened somewhere with the 2001/2002 year. I have a solid plexiglass hatch, and it seems to be ok so far.
Roc-
Roc-