I think unless you have the specific training and facility to perform an artificial enseminasion, you shouldn't attempt it. And by training I mean more than reading a couple articles online. Even then, the chances of it taking would probably be slim to none. The problem with the split in genus isn't about getting the two turtles to mate, it's about the differences in genetics that will prohibit the one species' sperm from fertilizing the other's eggs. I'm all for captive hybridization, but some things just won't work together.