First off, UV light is absolutely unneccessary for a brazilian rainbow boa. They get all of the nutrition they need from the rats they will be eating. The only reason you need to consider lighting is if you want to show off the cage colors during the day. (your snake will be hiding so the light won't show off the animal's colors).
I prefer to heat the animals from below with "Flex-watt" brand heat element. It's paper thin and easy to set up. I don't use lights to heat because it seems like a waste of energy. The snakes don't climb that much and they certainly don't hang out in the branches so there's really no need to heat the air. Brazilians spend most of their time curled up under their hiding spots. This is where I like to regulate the temperature. Whatever you use to heat the cage, I highly recommend using a proportional thermostat to regulate the temperature. I like the Helix DBS 1000. From what I've heard, Spyder robotics makes a nice unit as well. I really try hard to convince people not to use heating pads with a low, medium and high setting. First of all, even on low, they can get up to 90°. Way too hot. Second, you constantly have to monitor the temperature as the seasons and ambient temperatures change. It's much easier to program 84° on the helix and rest assured your snake won't overheat.
As far as bedding goes, there are lots of options. I have had success with newspaper, paper towel, pine shavings (aspen included), shredded coconut, and my new favorite, a western fir mulch that has a nice reddish appearance. My only caution is to stay away from cedar, or redwood. These woods are known to contain chemicals that can cause respiratory infections in snakes.
I agree with the previous post on the temperatures, but I have a different opinion on humidity. I spray babies and yearlings daily to every other day in the morning and let the humidity subside throughout the day. If I don't do this, they may have problems shedding. Juveniles and adults rarely get sprayed at my house and I don't keep any wet moss or humid hide box in the cage. I never measure the humidity and don't think it's that important for older animals. I do keep large water dishes in my cages so that the snakes can soak if the like. I've noticed tat when they are about to shed, they will often go for a soak. They will also use water dishes to thermoregulate on hot days or during mating season.
I hope some of this is helpful. If you haven't yet, please take a look at my website. I have an extensive section on captive care for these animals. While I wil be the first to admit that there is not one correct way of keeping these snakes, the info on my site is based on 16 years of experience withthese animals. I'd really like to help people enjoy these guys and to avoid some of the mistakes I made in the beginning.
Finally, if you'd like to shoot me an e-mail, I'd be happy to send you an e-copy of a care sheet I wrote. Wow! I didn't realize how long that was. I guess it shows how much I love talking snakes. If you have any more questions just let us know.
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Mike Lockwood
www.tooscaley.com