My bulbs are in the bottom. While mine came to thermal equilibrium eventually, that does not mean thermal uniformity. There are definite cold spots and hot spots in mine even with seven bulbs spread evenly across the bottom. But it doesn't take much of a fan to circulate the air just a little bit and even things out. I highly recommend it. Mainly because it will ensure your thermostat or thermocouple is in the same temperature air as your bow.