Hi John,
We have been flying a '59 Ares for over 10 years. The key to any of Billy's planes flying well is to keep the weight down as much as possible. They usually have thin airfoils and will fly a touch faster than most other Classic planes. 40. oz is a great weight to shoot for. Much more and the wing cannot produce enough lift to keep the model from mushing around.
A Magnum 36 XLIIS, Aero Tiger (my favorite), or other good modern engine helps, but a Fox 35 will fly the pants off of one if light enough.
Mongo