What do you think about these boating type of hatches installed in the roof. They are designed for ocean going boats so you know they are made well. You can order a bug screen and shade.
Because my roof is domed and the hatches are made for flat surfaces, I could fill in the space with some wood cut on a band saw and some sealant.
My roof joists are 24 inches on center so I could use a hatch thats 20 x 20 inches or so and wouldn't have to cut the joists. Install 2 or 3 of them. I could use them as an escape hatch if necessary.
But I still like the translucent roof and then put some hatches in it. The amount of light let in is really nice.
http://en.lewmar.com/products/index....id=1&page_id=4