I recently bought a 40 gal breeder and bought a cover that was supposed to fit but it's about 1/8 of an inch to big. I'm looking to get a cover cut but was wondering what would work best. I know acrylic and cheaper glass warps or bends and so I was thinking polycarbonate. Please Let me know if this would work. I was thinking either 1/4 or 1/8. Any feedback would be great thanks. So far the cover hasn't caused a problem but I'm looking to add an Arowana and they have a reputation for being jumpers. Thank you.