I'm kind of in the same situation. I'd like to install a 55gal sump under my 125 but I'd have to remove the middle brace, which is 2 2x4s screwed in with 8 long screws from the top and bottom. The only way to remove it would be a saw, which I fear would put too much vibration on the tank and could possibly cause a catastrophe. I think I'm just going to measure and get the biggest sump I can fit, or get two and plumb them together.
In your case, I've seen where they build a large arm that comes off of the center to suppor the center brace out further while the sump is installed. It's a risk but it might work.