OK! Tomorrow I'll try the new fix! This is what I bought for my mad experiment;
It's the Original JB Weld, and it had the highest PSI, the longest drying time, and is good for metal, pvc, and plastics - so it should work providing the force of the bowing isn't too strong. Being a chicken, I'm going to leave it clamped to dry for a week, not 24 hours - haha.
I bought the 4" x 4" T braces for the most coverage (that was the largest they had, and any bigger would have been wider than my rim anyhow). The flat brace left a big gap between the rim and itself, because my rim is formed in such a way that the braces dip down below the level of the actual rim. I took a hammer to the brace & reformed it as closely as I could to conform to the plastic. Hopefully it's good enough. The pic shows it laying over the good brace. Excuse how filthy the top of my tank is!
Now my next question; the way the steel clamp is, it pinches the plastic in onto the glass just because of it's sheer force to stop the bowing - the plastic is weak so it bends to conform with the clamp pressure. I have two of these long clamps and I'm thinking I could use them together - just far apart enough that the plastic rim isn't distorted while the whole thing sets up. If I just leave it clamped like it is (one clamp dead center over the brace) I worry that when I take the clamp off the "release" as it were will put extra strain on the joint and it may pop again, since the outer rim isn't straight now. (that may be part of my previous fail too). Does that make sense or was my description as clear as mud? lol