yeah put them at least 2 inches above, past that the lumens don't penetrate the leaves as well.
I can also say that 2 inches is a great distance with your light question, I did it, worked like a charm. You can get those lights SO CLOSE, it's just, they aren't warm enough to burn the plant.. and since they are a linear light source, the plants will flourish. I have found that warm white bulbs is the light they respond to best (they hated cool white, HATED)
------------------------------------------------ (big tube of light)
------- (instead of a grow light which emits from a small point)