Hatches on 28.5
No one seems to be responding with experience on a 28 ; however, for what it's worth, the earlier 28.5's all had a mid bay operable hatch in place of your 'skylight'. I replaced the original plastic hatches on a 28.5 with a Bomar low profile aluminum framed hatches; I believe the mid bay opening was about 9" square and the Bomar may have been about 9.5" at the frame flanges so I had to slightly open up the 'hole' edges with an orbital sander, then re-seal the plywood edges with Marinetex. If you have a finished surface inside the fixed plexiglas skylight, I'd measure that opening and match the closest Bomar size to it. Open it up slightly if necessary, provided you have at least one inch of flat surface all around the outer topside edge of the opening. Pilot drill and use a countersink bit at the new screw holes so as not to chew up the gel coat and set the hatch flanges in Life Caulk with newspapers set up below to catch what drips out. It's easy enough to use velcrow strips and fabric screening to make an inexpensive removeable screen to get the most out of your new ventilation improvements. good Luck!
