You will lose a little bit of light using the legs, but not much. Some folks have had problems with the PCs breaking glass because of the heat, but I can't imagine that one 28W bulb would do it. Usually I hear it from people with 96W bulbs and such. If you're worried, but also don't want to lose any light, just find something to raise it up 1/2 inch or so. I use the little plastic bumpers they sell for electronics to keep them from scratching your shelves up.