question on glass/acrylic/possibly polycarbonate thickness

[brianhellno]

I'm looking into building a plywood tank. Dimensions would be 8 feet long by 3 feet wide by two feet tall. I was wondering what the thicknesses should be for glass acrylic or maybe even polycarbonate. It would have one viewing window on one side and the window would probably be 2 feet high by 4 feet long. Maybe longer depending on prices. If it was acrylic or polycarbonate I would bolt it to the front. For glass I guessed most would recommend 3/4 inch for acrylic I'm assuming half inch and for polycarbonate I'm not sure. I don't see a lot of aquariums using polycarbonate so I don't know if its a good idea to use it. I just wanted to get others opinions before I picked out the thickness. Thanks to all.