I am looking to buy a fixed frame 16:9 high contrast screen (Da Lite probably). I know these come with a black masking border and optional fabric to absorb light overspill. My question is, when deciding what size screen to go for, do you measure the maximum image size thrown by the PJ, then buy a screen exactly that size INCLUDING the black masking border, or is that black border on top (outside of) the image size? Is it intended that the image actually overlaps the black border on the left and right sides (i.e. should the left and right edges of the projected image touch/overlap the black borders or sit inside them? Equally, if viewing in 4:3 mode, is it intended that the picture overlaps the black borders on all 4 sides? I just need to know exactly what size I need, and if I need the optional pro-trim finish at all etc. Thanks all!