FWIW, I was given a 55 with a crack in the middle brace. I tried filling in the bathtub, and the front, and back glass spread to about 1/2" wit the tank less than 3/4s full (as could be seen from the distance between the 2 pieces of brace).
Please don't do it.
Absolutely Not! The rim and brace are there for a reason. You tank will certainly bow out and eventually you will have 55 gallons on the floor. You can take the rim off of a 5 or 10 gallon and some have taken it off of a 20 but anything bigger and you are asking for trouble. I had a 55 with a broken brace and it indeed bows bad. I tried to repair it and it still bowed. I have heard of people getting their lfs to order a new rim for them. I just bought a used tank instead.
yeah a 55G will Deff bow a lot. I just replaced my top trim on mine(center brace cracked) left it 1/2 full the whole time. Its kinda a pita to remove the old frame. You can get a new trim from a couple places in black, not sure on the "oak" trims. They all are "perfecto" style.
I noticed that I see a lot of planted tanks without them. Looks nice. I see them in all sizes like that. how do they do it? I even saw a 130 gal. like that. My 130 doesn't even have a center brace, none of the old ones did. I'm a little scerd myself though.
LoL... Thanks for the comments guys. I know of a 55 that was missing the rim and it is still holding water 7 years later. I had an offer to buy it but I wouldn't trust it after moving it. It was a thicker glass than the one I got now though. The one I got now is a walmart tank and if you flick the plastic hard enough it breaks, no joke, did it.