Now that the ban is dead, I like many others are looking at building an AR pistol.  I still have an unbuilt carbon fiber upper and lower that I haven't done anything with yet.  What I'm thinking is to put a short buffer tube on it instead of the shorter pistol buffer.  I keep reading about reliability issues with the pistol buffer.  

But to my question, if I were to attach a sling stud to the back of the buffer tube and put a loop sling on it, is that legal?  By pulling forward against the loop slung around my shoulder I would effectivly create a tension to steady the pistol.  My assumption is that the sling would not get me into SBR territory, would you dissagree?  Can you support it either way?