So rather than tweaking the script everytime or doing more math each time...
In my case, I use the ruler as Young46 does which is always based on the view from the player and the ruler effectively sets the angle (not distance) in this view. The scale is set once in the script based on the screen resolution (matching to the aimer size in the player view). Only if I use a different screen resolution do I need to change the script.
Even so, I do have a seperate cell in my spreadsheet to change the specified ruler measurement if I use the other screen in my setup - basically like you described. It is a one-time change for playing on that screen.
I also have a separate output for ruler setting if I am using full spin, either top of back, since it reduces the actual drift in flight.
Rulers are a handy way to account for wind drift.