Bear... I think he wants to put the sump through the back by taking out the center back brace. And if this is the case... I would say 100%
NO if the tank is still full. Stands are made only strong enough to hold the weight of the tank and water. Some from
LFS's stands aren't even strong enough to hold even that much
There are ways to reinforce the inside so you don't have a center brace, but you need to be handy with tools, and you'd have to drain your tank first. If you want it in there that badly... drain the tank like you would be going to move it, take the tank off the stand, and carefully take the brace off. Depending on the stand that you have, this may be easy, it might not be. But at the end of the day... you want that brace back in before you fill the main tank back up! Don't attempt under any circumstances to do this with a filled tank... too risky for the rewards
IMO.