That's some good input and also good advice about the size recommendation : )
Honestly, I'm thinking to use several FX6s, lined up along the back, sitting high on blocks. The sump and its pumps might be too noisy, costly, etc. I was gonna use a 24" stand.
What type of mechanical filtration did you drill for on top? Before I purchase, I'll definitely want to see pics of the top of tank, to make filter and access modifications. Most acrylic tanks have a wide lip all around, partially for support, which restrict direct access into the tank.
I'm gonna check out some of the larger tanks sizes at the LFS to get a visual on height and width. Considering the options, if you had to do it over again, would you still go 4ft x 4ft? Also, thanks for sharing your tank pics earlier.