JEM Watercraft

I am building a stripped Northwind. I would like to add a viewing window in the bottom, just forward of the seat. Does anyone know of a plastic that would be scratch resistant enough to serve the purpose. I took a piece of plexiglass and with only a couple of strokes with sandpaper, I could no longer see through it, even on the water. That told me, the first time I landed on a beach plexiglass would be ruined. Glass is more scratch resistant, but I can't bend it to conform to the hull. Any suggestions?
Thanks
Jesse

Can't suggest another plastic, but as a last resort, how about a sliding cover, perhaps controlled by cords on pulleys?
Or how about smaller sections of real glass cut to conform better to your hull shape?
Now maybe real glass is scratch resistant, but as you know it does tend to crack or shatter in certain scenarios, which might have an adverse affect on your freeboard measurement.