Hey McCheeze, your going to want them about as close as you can get them. Seedlings and small clones 12" is ok but you can go as close as 1-2". I've had plants grow right into the lights many times with no problem...slight burning at the most.
Actually I just realized you have T12 and I had T8 so i'm not 100% sure the heat output is the same so be careful. As close as you can, where your hand doesn't feel uncomfortable.
T12 are pretty old and inefficient, i've replaced all my fluorescent lights with 1 600W HPS but it's dimable so I turn it down for the fresh clones and start of veg.
<=== My profile pic is lit by 8 T8 32W bulbs.
Cheers,
Silverserf