I thought it was pretty standard for the door to pop open on a Piper. It's happened to me multiple times in PA28 and PA 38's... I used to think it was something I was doing wrong. DAmn thing always seems closed and locked until you get to about 500 feet and then "thunk" and the roar of the slipstream (even at a mere 70 knots in the "climb") is enough to drive you nuts.
The two coppers should have just pushed HC into the void, that would have stoppered the gap and shut up the noise for a while. Oh, so long as her head was facing outwards, that is.
Suprised an Aztec carrying that much weight can get in to Paraparaumu. Bet it scared the tourists in the little tea rooms.
VHCU