Hello Gage, this is actually a good question and I've heard it before with various responses. In my mind, you have to ask yourself why do you want to do it? I know in their natural range where various subspecies over lap there is breeding with fertile offspring produced and some unusual patterns which people find attractive. A quick Google will show examples not only of intentionally captive bred animals but also photos by herpetologists on their various field trips of wild, naturally occurring cross.
Years back, I knew someone who had a female S.s.s. and these were the days when few animals were actually available. He got hold of two male S.s.t. I believe and cross bred them. He then took an F1 youngster most similar to the S.s.s. and crossed it back to the mother. I think the idea was to increase the stock of the S.s.s. The project was sold on as White's tree frogs became the new big thing. Personally, I'd never cross subspecies and I'd not encourage or recommend it either. If I were ever short of a mate for a single animal, I'd wait it out given their longevity.
