Catching Spies--
What you describeis perfectly possible. Essentially you played the fight right into the P-51 driver's hands, and the guy in the 51 apparently knew what he was doing.
First off, the P-51 can dive quite well. Given a 2K alt advantage, it WILL catch an LA7 and the LA7, despite being faster at low altitudes, will nto pull away unless in a prolonged tail chase. So it comes as no surprise to me that the 51 could close the distance.
One thing the P-51 does NOT do well is remain stable in these high speed dives--it becomes rather upset with the pilot and if he isn't careful the plane can rattle itself apart.
Second, the chop-throttle maneuver is not a good choice when you have an agressive Mustang on your 6, because the Mustang can slow down a lot faster than the LA7 can. All the Mustang pilot had to do was cut throttle, drop as much flaps as possible, and give in a liberal amount of rudder--when you do this, the P-51 slows down as if it just dropped anchor and I use this tactic myself on occasion.
There is absolutely nothing wrong with losing in the situation you describe--the guy in the 51 started with the advantage and managed to win.
J_A_B