So, back to my earlier advice. The easiest way to have exact temp control is to make the room cold and use a digital johnson or ranco temp controller set to heat and wrap each fermentor with heat wrap and use a thermowell. In my cold room, set at ambient 34 degrees, I can ferment a lager at 50 or a saison at 80. Works like a charm. I used to ferment 3 bbl plastic conicals this way.
That sounds like a good plan, but a bit more complicated than I want to do. We now have 16 buckets fermenting in there, and a wrap around each one would be hard to manage. I did get a bunch of those stick on thermometers that Tom mentioned, and before I left for work this morning, all 16 were in the 64-68 degree range. I'm happy with that. The 64 degree ones were all on the lower shelves. I think I'll get a small wall mount fan, just to move the air around a bit.
So far, this little room is working out nicely.