Just an additional thought. The planes you mention were early BPA-era planes. They had to fly on rear-exhaust pipes and retracts to get that performance. The flying style is also somewhat different, hence the name BALLISTIC PATTERN, with much faster average speeds, and larger maneuver size. The SPA planes on an OS 4-stroke can approach the large maneuver size of the BPA planes, but they still fly slower, more constant speed maneuvers.

I had the unique opportunity to observe both types of planes together and back-to-back last year at the first BPA contest. It was a real mix of the old and new(er). The 4-strokes on most of the SPA planes allowed them to perform larger maneuvers along with the BPA-vintage planes, (although somewhat slower). Without the 4-stroke, maneuver size would have had to be smaller.

BPA rules are less restrictive...even allowing brand new designs to compete if they are within wingspan and engine limitations. BPA is all about performing the older style non-turnaround pattern maneuvers with high-performance planes and engines (with a pipe), retracts, and with all of the characteristic sights and sounds that go with them.

I think "Vintage" or "Classic" pattern is divided into these two distinct eras, (Antique SPA 1962-1966, General SPA 1966 or so until 1-1-76, and BPA from the early 70s until 1996), and although there is some overlap, the January 1976 cutoff date seems about right as the division between the two.

Duane