Returning to the first post (and I'm on dodgy ground here without resorting to textbooks) although the Firefly has a high aspect ratio, so you might think the rotational momentum would be higher, this also has the effect of slowing the spin which would reduce it ( think ice-skater's arms). Different Fireflies have different fuel tank arrangements - the M's have fuel in the wings and the A, B, C etc. in the fuselage - which affect the nature of the spin ( flatter/steeper etc.) but not as far as I know the recovery except, as BEagle mentions, in the case of fuel imbalance.
The rudder effectiveness question is not really valid as the Firefly has a very effective rudder - the M260s have a ventral rudder extension to compensate for the longer nose - however what can happen in the case of incorrect recovery is that if the stick is moved forward before rudder is applied the down elevator will shield more of the rudder from the incident airflow thus delaying the recovery. The POH mentions moving the stick back then forward again in extreme cases but I've never known that to be necessary. In addition the nose with it's heavy engine will be lower and thus nearer to the spin axis, increasing the rotation rate - think skater's arms again. The main problem is that high rotational spins can result in very high rates of descent, around 6-8000 fpm in the Firefly although I was told of Bulldogs achieving
12,000 fpm during CFS trials, which seriously limits your thinking time.
Oh, and all of my Firefly spinning was done with the parachute option
.