When I do use a lamp for more then viewing/light regulation, normally in winter since this is CO, it's only for boosting the ambient temps. If more heat is needed on a cool side, say...another UTH should be used rather then a lamp.

I have lamps with dimmers built in or plugged into a dimmer and hang the lamp at least 8" above the enclosure top. I use 25, 40, or at most 50 watt bulbs depending on how much ambient boost I need, and then tweak between dimness and height of the lamp until I get the right temps.