I'm virtually certain that there is no measurement requirement. And I am certain that there is no provision to exclude any airplane for "design change" reasons. It's perfectly legal to take your Impact to a contest run under PAMPA rules, say it's an Ares, and fly it. And if your classic contest doesn't include Fidelity Points, there's no penalty.
It would also be pointless and you would not make a lot of friends, since it defeats the purpose of the event.
Brett
Rats! I've been holding back on this one, but locally have been making the same point: Enter your Impact in Classic, claim it is an Oriental, no penalty whatsoever is possible unless the judges are using Classic-specific score sheets, these including a section for fidelity points. In that case you're pretty much zeroed out on the 20 points possible, but even here in the NW fidelity points are not judged/awarded at all contests.
Of course, peer pressure would preclude any but the totally insane from pulling above trick, but that's the way our Classic rules read, like it or not.
As to dropping parts during flight, it was very surprising to see how completely incorrect was common knowledge. We even had a fellow DQ'd from an event in late 2003 for his muffler falling off during a flight where he had already taken an attempt and was merely screwing around. One of our very best judges made the call. Although I knew the full story as it relates to Howard, I'm not much of a fan of flying mufflers, high-speed touch-and-goes, latter leading to former, so I put a lot of extra attention into prepping for my own flight.
Shameful conduct toward a really good friend, but there it is. I did help look for errant muffler, however. What a guy...