That is a very helpful video for us scratch builders! I'm going to incorporate an inspection system like they used.
I had heard that the Piper builders used a larger tip and rod than what might be typical now. I've been doing the same thing and was happy to see it in action.
He likely wasn't too concerned in getting out. If it had been an experimental flight test they would have had a door ejection system for the purpose. In those days it was a CAA (now FAA) requirement to wear a parachute when performing certain aerobatic maneuvers.