Yes, the AC is based on Part 23, but there are essentially the same requirements for CAR 3. Remember that back in 1965 when they switched from the CARs to the Federal Aviation Regulations pretty much all they did was renumber what already existed in CAR 3 to come up with 14 CFR 23. There is also CAM 3 which is like the current AC system, it tells you one way you can comply with the regulation. For compliance with CAR 3 there is no real requirement to provide any performance data, just that at the time of certification the test aircraft has to meet or exceed the minimum climb requirements set in CAR 3.85. Remember, under CAR3.777 there was no requirement for a manufacturer to supply a flight manual for aircraft under 6000 lbs. Piper elected to go the flight manual route so that is what we are stuck with. CAR3.777(g)(2) says they should provide "normal rate of climb, balked landing climb at various altitudes and temperatures." When modifying an aircraft, all you need to show is that it meets at least what is published, no need to go beyond that. The aircraft can perform better but can't perform worse, if worse you would need to publish new performance data. As for actual performance data on a modified aircraft, if you are getting down to that level of granularity in your flying, do the testing yourself to see how your aircraft performs.