Aw damn that's horrible. Poor fishy. The BRS screen material is great. I have a ton left after making a cover for both my 75 and the 10.
I may go a different route. My canopy is open in a half circle on top (that's not how he got out though...the back is all open). One thing I like about the open top is the ease of feeding without having to remove anything. If I build a screen top I'll have to take the canopy and screen top off.
I have a piece of glass that is about 6" wide by the length of the tank and it covers my corner overflow and goes all across the back. Fish can't jump
right out the back, and because of the canopy they can't jump out the sides or front either.
What I'm guessing happened is he jumped and landed on the back glass. Then he flopped about, but in the wrong direction and instead of going back in the water, ended up on the floor behind my tank. Ugh. Poor guy.
I think what I'm going to do to keep my top open, but escape proof is...I have a roll of gutter guard that I used to block off my overflow. I'm going to build a fence of it that runs the length of my tank, but perpendicular to the glass that runs along the back 1/4 of my tank. The only way a fish could jump out would be to jump out and bounce off a bunch of surfaces to even get anywhere near a place that would allow escape. That will keep the front 3/4 of my top open.
You can see my overflow on the left in the pic below. The glass sits inside the lip of the frame, over the overflow and goes all the way across the back of the tank.
And then my canopy is cutout for the light. Front and sides prevent escape, but not the back...