Mike, did you use 3/8 thickness or 1/4 thickness acrylic? I did this with 3/8 thickness and you're right it's too filmsy. However, I siliconed a piece of wood in the back of the cover to offer support and that worked. It would work best if you can find a sturdy plastic yard stick, cut it to the right length then siliconed to the back of the cover. I was able to run HBF filter and still use the cover. When I have time I will get 1/4 thick acrylic and try to make the cover. The size of my cover are 27 x 15