Cool! *There's even chase-plane video of Cessnas doing spins. * *Some of
those guys are starting at 5,000 feet indicated or lower, which seems
insane. *I'd think you'd want to start at 8,000 or 9,000 just for safety in
case things don't go as planned. (cockpit object falls under the rudder
pedal or something)

-c

I wouldn't argue with 8 or 9 but 4500 to 5000 is okay for 1 spin in a
152 -- however I've only done 2 with my instructor.

The 152 AIM says 1000 feet for 1 spin entry to recovery.

However, "On the other hand, a 21-turn spin in the C-150 Aerobat took
4100 ft" (==195 ft per turn average).

Here is my primary instructor and her buddy doing a 52.5 turn spin in
a A152. They count off the altitude and the spins. You can see the
altimeter unwinding, and it's about 195 feet per turn, as Kershner
says in his Aerobatics book. You can almost make out the airspeed in
some frames which looks like it might be 40 or 50:

http://www.youtube.com/watch?v=IsX2yGJ2Tn4