I recognize your project.
I didn't have any adhesive at the top of the panels. In fact, some of the screws there were loose and starting to fall out. The panel was actually loose at the top. On mine, those screws went into a "bump" hanging down from the deck. It appeared to be a piece of fir that was glassed under the deck to give a fastening point to the screws and the holes were beginning to strip out from the panel flexing. It could be that somebody had remedied a similar situation on your boat by using adhesive and reinstalling the screws.
You might be able to slide a putty knife in from the front and see what you're up against. I used a putty knife and razor knife all around the floor because I had a bead of mostly failing caulking there, but no caulking where those screws are.
I assume that you have already removed the four rivets at the top of the panel aft of those screws?
When I replaced my panels, I had to inject epoxy putty into those screw holes to make sure that I had something for the screws to hold on to. I've pounded the boat pretty good since then and they seem to be holding.
Mark