A newbies impression of the 109 and spit

[Crumpp]

Can you explain to me how fitting a bob weight would correct an aerodynamic problem?

The fitting of bob-weights does not fix the stability issue. It compensates for the stability by increasing control.

It artificially increases the stick force gradiant. This makes the rise in stick forces as we get farther away from our trim point steeper.

In short, it makes the stick heavier so that it takes more effort to move it that 3/4 of an inch.

"suffers from quick changes of trajectory along the vertical axis, coming from high longitudinal thrust momentum, and significantly disturb aiming"

Right, it is a twitchy airplane under certain conditions and steep turns was one of them.

So was the impact of the inertia weight a double edged sword?

Yes it was a double edge sword especially for veteran pilots who grew accustom to a two finger airplane.