I haven't flown a puch, but I have been in a flat spin
in an SF34 with an instructor some years ago. The instructor
had decided to see how many turns we could manage in
a spin (note that after 3 you become a test pilot).
We were at 6500ft when we entered the spin. After 10
turns he decided to recover, but the spin was already
completely flat, with the nose gently nodding above
and below the horizon as we turned. Upon application
of the recovery control inputs, the spin continued
for another 3 turns (which gave plenty of time to start
worrying and thinking about the parachute) before we
eventually recovered. Unfortunately I never noted down
accurate start and finish heights in my log book, but
I think that we recovered at about 3500'. Needless
to say we never tried that again, and I wouldn't recommend
anyone prolonging a spin beyond 3 turns.