If you can't overcontrol at high speeds or in turbulent conditions then you'll get sweet F-A control at low speeds.
Terms to look up are Maneuver Speed and V-Speeds.
Going from flight sims in the past, maneuver speed being the fastest you can pull full stick deflection on ONE AXIS is about 240-250 mph for the P-51. By 360 mph it's -probably- not safe to pull half way, I leave it to someone else to guess why.
Note that in WWII fighters the pilot can't take what the plane can. They had feel and were less prone to trying things that gamers who have no feel take for granted. Also that IL-2 is a simulation. When some G-limit (like 12 G's) is reached even momentarily it is bye-bye wings. Pilot blackout though seems to have a time element.
BTW, I just came across FreeChecklists.net. Here is the P-51 page:
http://freechecklists.net/Resources/.../P-51+Mustang/
And from the 1944 manual on page 19 under Maneuvers Prohibited:
"It is impossible to do a good snap roll with the airplane and most attempts usually end up in a power spin."