The Chipmunk had anti-spin strakes added to the rear fuselage in RAF service to assist with the recovery if my memory serves me correctly...?
And regarding the parachute, someone above mentioned training. I remember well flying in Chippies are a humble (yeah, right!) Air Cadet and watching the "Jump, jump, John" cine movie of how to exit the aircraft safely (I bet that brings a few memories back!).
So with new passengers it's just a case of a thorough brief. That segment on the video only ran through it once.
1. Undo your harness, making sure it's only the one connecting you to the seat. (If they had to mention it, then it must have happened...)
2. Disconnect your bonedome R/T connection.
3. Open the air distrupting flap on the canopy.
4. Slide the canopy back all the way.
5. You'll be leaving to the left.
6. Stand up in your seat.
7. Turn around and step onto the trailing edge of the wing.
8. The next step should be into the gap, aiming about 3 foot behind the wing. Don't just jump from the standing start as you'll hit the tail.
9. During your ensuing descent, look for the D-ring. (Lots of gruesome stories about fingers worn away on webbing straps...)
10. PULL IT!!!!!
11. Knees together, legs bent, like jumping off a 12' wall.
How I remember this stuff I don't know. It's about 12 years since I saw it last.
But, I think (I hope!) it demonstrates that a full briefing will be remembered by your passengers...!
- It never really mentioned how a 4' cadet was supposed to turn around in their seat against the wind and then "step" onto the trailing edge of the wing, when they'd had to be lifted over the bloody side in the first place getting in!!
Still - it was great fun, I wonder if the Grobs today make you think it's proper RAF flying? There's something about taxying out in a tandem seater and doing aeros...!