That was why I suggested making the sump 1/2" smaller--before I realized it was just plain the wrong tank. I had an idea for a small setup that I was going to use the 12x12 for but when I got this tank it kind of went out the window. I even measured the tank. You would think I would have said something like "wait a minute" but nope just assumed I remembered the dimensions incorrectly...Probably needed to be an inch smaller on the back side for those 10" cubes. The 12" is right at that limit for size on the back being to much I think.
Still very nice quality tanks. I'm sure they will hook you both up with the correct size!