[RedDevil]

Good catch, should have added that wiki link myself.
Extending the bow length would help, but has issues discussed in the wiki page.
The bulbous bow produces the same gain as a longer and sharper bow but at lower cost.

The area rule should be effectice at any speed, but at everyday driving speed disrespecting it won't destroy your vehicle nor cause total loss of control.

When calculating the area you will have to account for other effects.
The air in the wake of your car, just in front of the nose and at the lower part of the windscreen moves at pretty much the same speed as the car and should be added to the calculated area.
You can turn it around and use the area rule to estimate the size of the pockets of air.

The area rule cannot explain all. Vortices, laminar flow, the Coanda effect etc influence air flow in ways that may defeat the area rule. For instance, many cars have rounded edges at the rear. In the wind tunnel the airflow close to the sides of the car will be turbulent because of the wheel wells and panel gaps and such. But a heavy sidewind will flatten those out so the airflow will be laminar at the edge, and curl around it causing drag.
Slightly altering the direction of the airflow hardly influences the area rule but will sharply raise resistance due to altered airflow.