danleon,

I think there is an effect like the one you describe. It seems to me that there was a thread somewhere here about Vtails a few months ago. If I recall correctly, someone posted a link to a rather involved paper about Vtails, and I think that I downloaded the paper, but I can't find it at the moment. It seems to me that the paper had a discussion about the drag and control surface effectiveness of Vtails, and I think there was a reference to the non-symmetric response you are experiencing. If I find the paper or the link, I will let you know. Try searching for the thread.

banktoturn