I'm a regular citizen, enthusiast.
RCS is combined effect of geometry, RAM, RAS, EW, etc.
For Westerners it's easier to make a custom S/w tool & do some estimation, that's very superficial bcoz different countries make RAM, RAS, EW of different quality/efficiency. So the public estimation might give a geometric estimation but remaining is top secret & whoever tries to get close would be cautioned & if tries to reveal it would be arrested on charge of espionage or treason, or mysteriously perish.