You asked for commentary on the Hanger 9 P-51 PTS. There was an entire thread on that a few months back (maybe even last year). The P-51 PTS has a number of flaws, primarily associated with poor quality control in the assembly process. I have maidened three of these, and all three had the same issues.

First and foremost, the landing gear blocks are not properly glued into the wings. This requires stripping back the covering and regluing the landing gear blocks.
Second, the cowl is not properly trimmed around the throttle. The stop for the low speed idle bumps against the cowl when the throttle is advanced, causing the low speed needle to be set to the full rich position. Low end tuning on the supplied EVO 46 is consquently screwed up every time you advance the throttle (until the cowl is trimmed properly).
The three bladed prop is a very poor match for the engine. It barely develops enough thrust to get the plane airborn, particularly if you're flying off grass. Ditch the three bladed prop and replace it with an APC 11X5. OK, its not as scale lookng, but when its spinning, you don't see it anyway.
Finally, as an instructor, I find it to be a very poor platform for learning. It flys like a pig with the training aids on, and is way too sensitive with out them. With the training aids, it promotes overcontrolling the sticks, and without them, its too hard for the beginner to fly.

If you absolutely must go with the mustang, you'll learn. But a high wing trainer will be easier and quicker to learn on, and will provide many years of enjoyment, especially if you keep in mind that trainers can be modified for many different functions. Their low wing loading, inherent stability, and inexpensive airframes make them ideally suited for addition of things like cameras, bomb drops, streamers, snow skis, floats,etc. They can be a real hoot at fun flys, and eventually become beloved "beaters", coming out of the hanger when other, more expensive planes get to stay home. And as you progress, hopefully to teaching some other niaive soul how to fly, they are great for providing demonstration flights.

Brad