There never was a " One Design " for IMAC. In the '80's the full scale guys dreamed up an class where all the guys competing would fly the same aircraft design. I think a couple prototypes and even a 2 place version called DR109 was built. The idea just didn't catch on. What the OP has is a kit modeled after the full scale One Design. It was either produced by Bob Godfry or I think Frank Noll had one too but not 100% sure.