I'm not sure why lamps should be necessary in a tub set up. One of the great things about tubs is that they not only seem to hold heat better, but that they also hold humidity really well. Once you add the lights, you're sucking out a lot of humidity.

On my 41 quart tubs, I use a one foot section of 11" flexwatt and control it with a Ranco thermostat. I don't use any lights.