As a former Hangar 9 P-51 PTS trainer owner (I crashed it on the 16th flight due to visibility issues and loss of orientation)
The P-51 was my 3rd glow plane.
I still stick to my guns and say it is not a good trainer.
I am not saying you can't learn to fly with one, I am saying for the average person it may take longer to learn and there will be some that wont be able to handle it and have to move to a traditional high wing trainer.
With the P-51 PTS I would strongly recommend buddy box traing with a qualified instructor.
There are some quality issues with the landing gear so be prepared to do some surgury on them. Other than that once you do get comfortable with the P-51 PTS you will find you have an airplane that can do all kinds of aerobatics with ease and a nice looking airplane as well.