The 2' x 3' Smart Panels in my house were installed one above the other, short sides up. Check your local building code, but in my area Smart Panels are classifed as low voltage hubs. But because my panels were each wired with household power outlets (for wireless modems, security system, etc) all I had to do was them away from water sources and make sure the outlets were up to code.
You can run all your household low voltage wiring (cable, satellite, security, speakers, internet, network cabling, etc) into these panels. This way, you can make changes to what rooms get what services without having to rip open walls to access wiring or run new wiring. A little extra expense but worth it, imho.