Sorry, I wasn't real clear about what I've got in my original post. I have the Hera Arms CPE kit.
http://www.thefirearmblog.com/blog/2...11-carbine-kit
I want to keep it configured as a pistol, no 16 inch barrel, no vertical front grip and no stock, but I want to add a single point sling attachment and would need an AR buffer tube for that, just want to make sure a buffer tube won't count as a stock.