When the C250 was first introduced, one of the first quirks to be identified was the need for careful attention to the balance when on the trailer, otherwise a water problem would result because of the rain gutters with the forward hatch draining forward and the main hatch draining aft. Also, the sliding hatch was prone to wicking the water back from the aft edge.
New owners quickly started making hatch covers and soon Catalina added a cover as part of the boats canvass package. Some or all of the Catalina production covers have been 2/3 covers which fell short of covering all of the pop hatch joint but they seem to work ok. If making one of these covers, I'd do a full cover so as to keep all air borne debri out of the rain gutter.
