The only problem I have with rubber is when it degrades over time, you need a new one. If there's any kind of stress on it, it'll decrease the service time. As you aren't enclosing it into a wall and leaving it exposed for inspection from time to time, go for it. But as somebody that likes paragons of work that can last almost forever, why not put an extension on the run and maybe use use a couple 45's? Rememember Murphy"s law: If it can go wrong.... ? Keep it simple and later down the road it won't rot away at a very inconvenient moment when there's something else to handle or spend money on.