I happened to have a piece of 1/8″ plywood scrap that was the perfect size to make a panel for the turtle deck opening. After cutting it out and varnishing it I think it looks great.
The slots are for the seat belt shoulder harness.
This does sick out past the rear spar carry through so I glued a block to take up the gap.
To hold the panel in place I glued a tab on the back of the top.
Two studs were added at the bottom to hold the panel in place.
Two thumb screws attach the panel.