I have spun the Chipmunk a few times with a very highly qualified chipmunk pilot in the rear. I have never dared to do it solo. Apart from anything else, I have wondered at the effect of the C of G being much further forward solo and whether there is a danger of going inverted when pushing the stick fully forward during recovery. I would be interested in comments!
Is the increased rate of turn not due to the nose dropping further and therefore the rotation increasing to preserve angular momentum? I believe the Slingsby has that characteristic.