Will, you beat me to it, I was just going to post about the competiton. It's at this gym:
though it is no longer called Stone + Axe. It's now underneath a Kolon Sporting Goods store, between K2 and KSwiss stores on a large street. You can get there by taking the 704 north towards Bukgu or Chilgok, going over a large river, then a smaller river, and then get off at the Dong-A Department store and walk back five minutes in the direction you came. Walking backwards, the gym is on the right side of the road. If you are looking for it on the bus ride up, you can see it from the left of the bus. There is actually probably a bus stop closer than the Dong-A store, but that is where I got off at when I went, so that's what I can speak for.