If you are a true beginner, I wouldn't recommend an inverted mount. I would say that it is much much more difficult to run an engine that is upside down than it is to do it in any other appreciable angle.

For beginners building an ARF for the first time, I would recommend a normal (right side up) mount. If that is completely not acceptable, go with the sidewinder. I had an O.S. 32SX that idled and flew fine inverted. My Towerhobbies 75 ran terribly inverted. Deadsticked all the time.

That's just my 2 cents.