Creating a hollow vessel tree

Hey there,
I am trying to create a vessel tree in Rhino. The vessel tree is built with bifurcations, means every vessel eventually splits in two smaller daugther vessels. Because we will need trees with up to 30 generations, I tried creating this tree with Python. It works up to a certain point: I want to use the vessel tree for flow simulation, so it must be hollow, with smooth walls and no edges on the inside. Whenever I try to hollow out my solid vessel tree, I fail because in the bifurcation area the walls of the hollow tubes collide. Has anyone any idea how this problem might be solved? Can I somehow create a skin over my model and then delete the model itself so that only the skin remains? Plus, it would be nice if the bifurcations would be really smooth, like a y-pipe connector to minimize flow resitance. I would be so thankful for any tips or ideas!