If you see stretching, you can lower light as close as your fans will allow you.

You need a fan solely to blow between the lamp and the canopy. Add an oscillting fan to move air around. With a fan blowing right between the plants and canopy place your hand right above the seedlings...lower your lamp 6" at a time until your hand gets hot! Move lamp up 2-3 inches and test again. If you can have your hand on the top of your canopy for a minute, withyout feeling HOT heat, then the light is NOT too close and won't burn your plants; However, you must monitor this height daily to keep from burning your tops. hope this helps. lw