hello Sag75,
the brightness of the ambientlightcolor (it is inside the envcolors.dats) is responsible for been spotted or not when you are surfaced at night.
in gwx, these values are setted too low and you can almost 'touch' the ship at night without been spotted.'play' with the brightness of these values and you can adjust from what distance to been spotted at night. the foto is from gwx3 with its own environment:
