The stacking option is what appealed to me.. but later on I built shelves for all of them. You're on to something by considering every other with an UTH because the tank stacking heats tanks above and below. It was really wonky for me as the inconsistancy of heat between each row was hard to reconcile. I also use the heat shroud, this really got the tank above cooking. That's why I went to putting them on shelves. By using a combination of UTH(on a thermostat) and incandescent lighting(on timers) with Vision set-ups, you get total control over the environment. Every outfit will be different though, as the temperature of the room and even seasonal temps of where you live will greatly influence controlled systems. Ya gotta tinker with it.
Good Luck-
Matt Schubarth
Pet Nebula