Hi friends, I believe that the crux of the question was what are the dates for eligibility for Classic Stunt? My understanding of the answer to that question is any plane designed, published ,kitted, of verifiable as having been around as of December 31,1969. therefore any Old Time plane of relevant pedigree would also be eligible for Classic Stunt per SE! Now Nostalgia Stunt is an entirely different thing since it incorporates a moving date or dates being 30 years old or older!
Viz. if you are more modern design focused this year would permit designs as of 1985 as back would be just fine! I suspect that you could even refine this parameter by date as in months of 1985!
Tally Ho!
Phil Spillman