I like it, very cool. Excellent design.
The only critique that I have is that there is not much left from the xbow. I don't in any way mean to detract away from this fabulous design, I just wonder if it would have been easier to adapt the Splitfire to a +bow? The +bow design lends itself to an infinite variety of potential add-on combinations. Perhaps you considered that option already and dismissed it for some reason?
I'm not asking the questions to be a dick, I asked because I have been contemplating a +bow/splitfire combo.
Check out the last post in the Homemade picture thread, Ryan McNumbers has a very nice example of the +bow splitfire combo you speak of (still not as beautiful as this though. Amazing work Slug).