I've been away from virtual pinball for quite some time now but a few days ago I found out that Stefan (Herweh) made the source code public.
I am surprised to find that the old screen selection "bug" from my original B2S code is still in there.
The backglass screen number that you enter into the screenres file is used in B2S to select the display with that number in it's name: DISPLAY1, DISPLAY2 ...
A better solution would be to use the number in screenres to select a screen from the screen order as it is defined by the user. Number 1 should point to the first display, number 2 should point to the second display and so on. Same method as the old UVP and probably also PinballX is using.
Here is a suggestion to any programmer who want to experiment with it. The screenshots are from the class B2SScreen in the b2sbackglassserver. Same changes must probably be made in the b2backglassserverexe as well. My changes are highlighted in the screenshots.
Only problem with this change is that the old B2S.exe files may be displayed on the wrong screen for some users. Could be solved by storing the old b2s in a separate folder with it's on screenres file.