Is this what your canopy looks like??
http://www.all-glass.com/products/hoods/versahood.html
How much is the glass out by? A long time ago I got a piece of glass to fit in the rim of my 10 gallon, it was a smidgeon too wide, I don’t know, maybe 1/16 inch. I took the back off the can opener, the kind with the stone wheel in the back for sharpening knives, and ground the end of the glass down. It seemed to take forever but it worked and I could keep trying it on the tank so that I could stop when it fit exactly. Now, your plastic middle part might be a problem, is that too wide too? I don’t know what you can do, unless there’s a bit you can pare off with a knife, or make a notch or two or something.
http://www.all-glass.com/products/hoods/versahood.html
How much is the glass out by? A long time ago I got a piece of glass to fit in the rim of my 10 gallon, it was a smidgeon too wide, I don’t know, maybe 1/16 inch. I took the back off the can opener, the kind with the stone wheel in the back for sharpening knives, and ground the end of the glass down. It seemed to take forever but it worked and I could keep trying it on the tank so that I could stop when it fit exactly. Now, your plastic middle part might be a problem, is that too wide too? I don’t know what you can do, unless there’s a bit you can pare off with a knife, or make a notch or two or something.