Two Sticks
I cut two pieces of teak (you could probably use anything, I just happen to have alot of it laying about my garage from other projects) about 18 inches in length and put a stainless screw with about 1/4 inch sticking up at one end. On the underside of the fiberglass cover, I drilled two small holes about 1/4 inch deep in the wood out towards the end. when I want the hatch up, one stick goes on each side, the screw in the hole and the other end goes in the rain gutter on the top of the boat. Gravity holds everything in place, even when big jackhole motorboaters go by pretending not to see you at anchor. I tried working something out using those stainless hatch props you get from WestMarine, but this was much simpler, doesn't require cutting or modding the hatch in any way, and when I don't need the props they just get tossed in the ledges behind the seats. I'll try to remember pics next time I go out.