I lived around Chicago for 22 years, so I think I know what you mean.
A 4-foot stand would be designed to hold a 4-foot tank. A 13 foot stand might not be designed to hold 3 4-footers. You have to make sure each of the tanks is being fully supported on all sides so they are not sitting unevenly or in the middle of a beam. Are they being supported evenly front to back as well?
Do you have a sump for the basement (I did.) In my case, my entire floor had a very slight slant to the drains. A 13 footer will likely show that.
I'd be concerned with potential wiring hazards, overloads or extension cords as you may have limited #s of outlets. Similarly, I'd be worried about doing a WC on one tank while another tank 1 foot away is turned on and operating.
I had multiple tanks, some next to each other and it was fine for me, although they weren't all quite that close.
