Hmmmmm, I have the same V-tail on my SS and also have a BL motor (one of the tower pro can motors - I barely fly above 1/2 throttle, and cruise at 1/4 throttle). I've never had any issues you speak of. In fact, like I said earlier, I think it flies better.

Mine was still rock solid stable with the V-tail. Is it possible you installed the V-tail crooked or something that may be causing it to create some instability? Maybe try contacting radical R/C. There's also a guy whose screen name is "boomerace" over on wattflyer.com who has tons of SS experience including with this V-tail. Maybe try shooting him a PM or alert him to this thread.