Steve, If you drill out the rivets then you can
remove the inside frame and see what is under it and what it is riveted to. If you are careful you can always put everything back as you found it. The thing to do is proceed slowly and figure out how they put it all together. You still have two months before it is warm enough to go sailing anyway. Keep comming back as you have questions. Pop-rivets with a 1/4 inch head usually are inserted in a 1/8 inch hole.