IMAC flies scale airplanes and somewhat replicates scale aerobatic maneuver sequences. The planes have no size or weight limit as long as they are within something like 10% of scale dimensions. IMAC has 1000' deep by 2000' wide box, but it is not enforced as best as I can tell.

Pattern requires that the plane will fit inside of a 2 meter square and must weigh no more than 11 pounds. Pattern flies a sequence of geometric figures on center(geometrically centered directly in front of the pilot connected by turnaround maneuvers on each end that must stay within "the box". The box is defined by lines that project out at 60 degree angles from where the pilot stands. The further out you fly, the wider the box. But the pilot is limited to a max distance out, anything outside of the box will result in downgrade.

If you want something that is good for pattern and IMAC try the Quique Somenzini 73?" Yak. Its fits the pattern specs and can also make IMAC as I understand it.

Differences is are IMAC planes are generally bigger and fly like scale planes. They are more stall prone but fly extremely well. Pattern Planes are smaller, sleeker, and built for purpose. They are more stable and can be flown a little more gracefully than a Scale aerobatic plane.

The general rules of judging are very similar for both, but have their own nuances.

Generally speaking.