This is a VERY long movie but in the beginning you can see that taking off is not a particular problem (but it took me several days to learn it though...a long time ago).
And trying some low speed maneuvering is not a problem either. So there's nothing wrong with my flight model, it handles as it's always been handling.
What it all comes down to is (just like somebody already mentioned), to learn HANDLING.
At low speeds.
For this particular flight, I don't bother with any trim or RPM-fiddling. You can fly for hours on end at full RPM as long as you manage throttle/watch the engine gauges and thus don't totally over-abuse it.
To conclude: I'd be the last person to claim I know the Mustang systems and what's "right", "by the book" etc but I DO know how it handles.