In 1972 I was a civilian Instructor with the RAAF Pt Cook Flying Club.The Boss was a Sqn Ldr Kevin Duffy, lovely guy but double my weight. I was around 60kg in those days. We took off with the primary task of checking my ability to teach spinning. He insisted on sitting in the back. At 6000' I entered a spin which immediately went 'flat' with the nose hunting through the horizon. The prop stopped and I had a difficult time recovering. We eventually recovered but busted the 'floor' of 3,000'. The aircraft was subsequently fitted with strakes before further spins were allowed. VH-RSK was the rego, belonging to Peninsular Airways of Moorabbin. He passed me but we both retreated to the bar to regain a measure of composure. The owner of Peninsular, a Dr Bill Surh also had a Ryan fitted with a 'flat' engine and had a tail parachute rigged, because the new engine installation effected the spin recovery to the point that the only method of recovery was to pull the string. To see that Canadian Chipmunk with a 'flat' engine and no strakes bought back some bad memories and thats why I'd be interested to know how it spins, or more importantly if it stops! Again if the Canadians never fitted strakes is it their canopy that keeps the back end alive?