Ask Frank about UV light at varanus.net. He'll school you on it.
And being high up in a canopy does not mean you are in direct sunlight. Tropical canopies can be very very lush and no much light gets through.
And just because you live in UV light, does not mean you require it. Many many reptiles use the sun's rays as a HEAT source and a heat source alone. The UV part is irrelevant.