I expected it to be do to some rationale along those lines, although a Killer Chaos is quite different than a whatever-Kaos... while a Tiporare, although designed flown in 1979 by Dick Hanson is obviously a Curare knock-off with slight differences and much closer to the Curare than the Killer to the Kaos. And many pattern planes usually start with modification of some design. Maybe the design year limit should be relaxed altogether and just limit it to NON-TURNAROUND designs... And by that standard it could be argued that the Dirty Birdy grandfathered the UFO, XLT, Grand Escape, etc. But I digress...