[Klemm]

Of course I do not know where the C47 (and L2D) bug is be so it may be too early to suppose its flight model might be defect - it could even turn out all three C47 variants might have same flight model.

The bug makes C47 fly like loaded with a ton or two of extra weight in its nose, or as if it had a badly damaged elevator causing its controls become very inefficient.

So the bug might as well hide in the balance of the C47 or in its controls or anything else related..?

Everything you described is defined in the flight model.
There are some subtle but nonetheless noticeable differences in the two FM's, i test-flew the planes and they behave very strange indeed.

(Note to mods: this is about flight models behaviour, not FM modification)