I like the idea of the single point method and it will allow perfect balancing both side-to-side and the CG. There may be a problem mounting the dowel or screw eye on scale models without leaving some evidence (hole or dowel). You have also got to mount the screw eye or dowel such that it will support the entire weight of the finished model. Most of my models are in the 8 to 15 pound range. This must be "designed" into the plane (most likely the wing) during the building phase. I would be a little nervous about hanging my Top Flight Cessna 182 (13 lbs) from a single point on the top of the wing. Large, giant scale models (20 to 35 lbs) would be a challenge.

However, the rope a plum bob method does not require the installation of the single point to hang the model from AND you can use bigger or stronger rope as required. You can hang the model from a loop from the nose and tail OR from side to side (wing). The nose to tail method will allow side-to-side balancing as MajorTom described.

Again, I am not a sales person trying to sell the rope and plum bob CG Machine. I just think it is a great method to finding and adjusting the CG and lateral balance of a model. I found a pictorial description of this "CG Machine" several months ago and downloaded the pictures. I lost the web site address that I found these pictures. However, I did post this pictorial tutorial on the CG Machine on my web site. You can find the tutorial in the iFLYrc Magazine on my site at:
http://iflyrc.hypermart.net
Enjoy!