I realize this post is getting a bit old, but I would like to add a few thoughts. I owned an M20F for 10 years, and used to practice stalls regularly. Even with the ball perfectly centered, the left wing would drop like rock (rigging?). The problem I have is that you must recover immediately, or you are really asking for trouble. Why push the edge of the safety envelope?
During the NASA general aviation spin tests in the 70's and 80's, Mooney's were one of the aircraft that entered flat, unrecoverable spins. The rudder is relatively small on Mooney, making spin recovery more difficult. If you get a chance read Rich Stowell's fantastic book "The Light Airplane Pilot's Guide to Stall/Spin Awareness" (2007). The first pages to read are 306-307, which discusses Mooneys.
Here is a quote from Bob Kromer, the Mooney test pilot for several of the earlier models: "Outside of practicing deep stalls and realizing how to control any tendency to "drop a wing" with the rudder, the average Mooney owner has no business doing spins in a Mooney. They use up a minimum of 2,000' per rev and outside of finding all those lost things hidden on your floor, the experience isn't pretty"!
2000 feet per spin revolution - think about it.
