Tony.

A couple of important points that have not been mentioned.

Generally, in IMAC the model has to be a scale model of an aerobatic airplane.
The outline of the plane can not deviate more than 10% from "true" scale.

The only exception to this rule is for the Basic class, where there is no scale requirement at all.

Therefore, for Basic, (in my opinion) the "Best" plane would be the one that flies the best. There are no model planes that fly better than Pattern models.
A 2x2 meter pattern model, preferably with an electric motor operating on 10s lipo, would therefore be best.
A "Profile plane" will fly the Basic program quite well, but not as well as a pattern model.

For all the other classes, it has to be a scale model.

Magne