You can't run a cliff up the side since it'll be a whole tile wide. There's a script for doing this kind of thing. I didn't use it, but I had the demo for a little bit, I'll have to come back to this later since I don't have time to go find it right now. It was
here somewhere and it was posted by Mr.A. It's been a couple months since I've looked at it, so depending on how popular it was, it might be on like page 5 or 1.