Using clear plexi or lexan for a section of the boards lets in light and lets you see out, so someone below can tell the helmsman about an impending wave, for example. If you're in a marina, translucent rather than transparent plastic can give you light with some privacy. The next trick is to make a section with screening, to keep the bugs out at night. Since they'll probably all end up under your bunk cushion, getting them all the same thickness (half inch, you said?) will likely make them less uncomfortable to sleep on.