I have been doing a simlar project on my own GUI, after our chat in "[TEC] telemeter Scale in the german optics" thats how I got the redmask idea.
I found you can change things quite a bit. You could make the display area a bit bigger in the camera.dat - camaraParams/Viewpoint to get rid of the marks completely.
Work is on hold at the moment, while I do the ships manual.