From an interview with Howard Baugh, Tuskegee pilot:

Tell me about your solo in the P-51.

The solo in the P-51 wasn't any problem because the cockpit and the handling of it were actually a little bit easier than a P-40. We were accustomed to flying the high-powered airplanes with the power that the P-51 had. That was no big transition. There were slight differences between the two airplanes. The main difference in the P-51 was that it had much more power and that it had a four-bladed prop instead of a three-bladed prop.

It had a lot more power so you also had to have more torque. On the takeoff roll with high rpm the torque would try to pull the airplane to the left. The P-51 had a steerable tail wheel. The rudder pedals were used to steer the tail wheel to keep the plane on the center-line until the airs speed was built up. The idea was to get up to enough speed so that you had air going over your vertical stabilizer, and so that you could maintain direction by using the rudder rather than the tail wheel. You had to get a pretty good speed with tail wheel still on the ground. If you didn't do that, the propeller would pull the plane right off the runway.
 

We had been trained in the other airplanes in stalls, to become familiar with the airplane and build up confidence in it. You'd get up into a power-off stall, a power-on stall, a flaps-down stall, a wheels-down stall, and stuff like that. So I was in a P-40 and wanted to go through this series of stalls and build up my confidence in the airplane and get familiar with it. I did all my stalls okay, and recovered from them. When you stall an airplane that means you get down just below the flying speed. You don't have enough forward motion to keep the airplane flying, so the airplane falls and you recover. So I decided I wanted to do a power-on stall. With the normal cruise power, I pulled the nose up and the airplane climbed and climbed and climbed. I got up to around 15,000 feet before the airplane stalled. Then the torque took over on the right, when the airplane lost flying speed, and put me into a violent power-on spin. It threw me all around the cockpit. I finally got to the place where I could pull the throttle off and straighten out the airplane. I must have lost six or seven thousand feet. It was a good thing I was that high to start with. Of course, I never tried that again! That occurred at Tuskegee, when I was still transitional in the airplane. I never told anybody about it, either.