Note, you can not decrease the RCS, indefinitely, because it gets harder and harder, after a while.
Wrong. The radar cross section ( RCS ) value is often called, by professionals in the radar engineering field, as a 'fictitious' figure.
It is fictional not in the sense that we just made it up out of nothing. The value is fictional in the sense that the value changes because of many factors. Some within our control, some regardless.
For example...
Let us be clear on the difference between 'stationary' and 'fix'. People uses the two words interchangeably in casual conversations and nothing wrong with that. But in critical categorization, how they are used in certain contexts affects design parameters.
A radar station can be stationary but not fixed, meaning the radar is not mobile but can scan in 360 deg. The typical airport airspace management radar is this type.
If the seeking radar is stationary but not fixed, as the aircraft transverses the radar view, beginning from frontal, which is the smallest RCS, to full side view, which is the largest, then to rear aspect, which is smaller than side but greater than front, the RCS value changes as the radar follows the aircraft's path.
If the seeking radar is stationary and fixed, as the aircraft transverses the radar view, there will only a brief moment of detection of the frontal aspect.
The RCS value, which is a data processing function of the receiver part of the seeking radar,
COMPLETELY depends on the reflected signals from the target. If the target is able to control those reflected signals to any degree, the RCS value changes accordingly.
The data processing function of the seeking radar is not within our control. But the reflected signals are absolutely within our control. The current method of affecting reflected signals is shaping with some assistance from absorber, which is materials control. We have done it to greater than %90 of degree of control as evident by actual combat experience. Shaping is essentially redirection of those reflected signals.
If we are able to achieve %100 degree of control of those reflected signals off the aircraft, the RCS value will drop to zero. At this point, there is a high probability that even quantum radar signals can be negatively affected.