Adding UVB isn't going to stress most snakes, as it's just like being outside during the day.. you do have to keep regular cycles though. Even giving your snake full spectrum lighting will give the snake UVB.
Here is an excerpt from a care sheet for Cali King Snake, but I think you could use it for Boa's etc...
http://www.reptileknowledge.com/care/california-kingsnake.php
Lighting Your Kingsnake Enclosure
"This lesson will be shorter than the temperature and humidity lessons, because it's a simple one. Here's the gist of the lighting issue:
Use a full-spectrum fluorescent light (one that produces both UVA and UVB rays, like the sun) to give your California king snake about 10 hours of light each day. Do this, and you'll be covering your bases in the lighting department.
For a long time, snake keepers have been arguing about whether or not kingsnakes need UV lighting for their health and wellbeing. It's really a simple matter, though. Once again, I point to nature for the answer. In the wild, California kingsnakes are exposed to natural sunlight on a regular basis. So why not duplicate this in captivity as much as possible?
For me, it's a no-brainer.
Remember, the more closely you can duplicate the natural conditions in which kingsnakes exist in the wild, the healthier your pet snake will be in captivity. This includes giving your snake a regular cycle of light each day (a "photoperiod"), using a fluorescent light specially designed to produce UVA and UVB rays.
Using full-spectrum lighting will also increase your own enjoyment as a snake keeper, because these lights bring out the true color and beauty of California kingsnakes (similar to how the sum does in nature). Kingsnakes are among the most beautiful of the North American colubrids, so why not let their beauty shine by giving them some full-spectrum lighting?
You can find these full-spectrum lights in just about any pet store in the country.
You can also buy a lamp timer at any hardware store (and even some grocery stores). This will make things easier for you. Just set the timer so that the fluorescent light comes on for about ten hours a day, using the natural rise and set of the sun as your guide. After that, it's a convenient "hands-off" process — the timer turns the light on in the morning, and turns it off in the evening."
