I have to admit being a bit curious about this creation. Will you change from right to left shoulder when you fire the left hand barrel, or is there some sort of mechanism which allows you access to the left trigger from the right side? I have to admit that I prefer the idea of changing shoulders. A video clip of your creation in action would be a big help.

This technique has some interesting possibilities. Mating a right hand bolt action with a left hand version comes to mind, or a couple of top ejection lever actions, perhaps? Combining two Savage Model 24's would give you two shot and two rifle barrels to work with, an instant Vierling!