The Visitor wrote

Was it the wing that stalled? Back then I was taught it was the
tail.
I was also warned if carrying ice to be _very_ wary of a tail stall
(no
flaps). As for the cardinal, pilots at the time told me the slots came
out because some people were managing to stall the stabilator. It must
have a very forward center of gravity, but to me that is the way it
should be to make loading easier.

Yes, I'm aware of the icing issue. When I first posted, I was
mentally referencing a NASA tail plane report that I had been reading.
They did extensive tests and showed that an a/c is most vulnerable at
the MAXIMUM speed for a given flap setting. Each flap setting
increases the negative AOA for a particular airspeed, due to the
downwash of the wing into the horizontal stabilizer. However, as the
a/c slows, the AOA of the horizontal stabilizer becomes less negative,
because the tail rotates down; the increased downward lift is provided
by the elevator deflection, rather than increasing the AOA. I didn't
stop to think how the report would differ if they were discussing
stabilators.

One possibility for the effect you noticed is that as the main wing
stalls, there may be a decreased downwash over the horizontal
stabilizer, which would produce a downward pitching motion.