Hi Shane,
You can fly your 'foamie' in basic if you want. ;-) There is no restriction in basic on the airframe. I CD the contest near St. Louis and have seen many competitors fly several kinds of planes in basic.
Cheers

From the 'Official IMAC' Scale Aerobatics Ruels, Flying, & Judging Guide
General Rules Scale Aerobatics:
3. Open Events
3.1. The events accomodate aerobatic monoplanes and biplanes which are replicas of types known to have competed in International Aerobatic Club (IAC) competition, or replicas of types known to be capable of aerobatic competition within the airspace known as the "Box".
3.2. All classes except Basic require that the pilot must meet the requirements defined in Rule 3.1. The Basic Class is open to all competitors with a monoplane or biplane aircraft. There is no minimum size requirement for any class. Contest Directors may make an exception for a model of a full-scale aircraft that was built for IAC competition, but has not yet completed. Proof of the latter is the responsibility of the contestant.