From what I've seen in a quick search, roller shades that mount inside windows don't completely block light because the hardware extends slightly past the window sides. The other option is to mount the roller blinds outside of the window rather than inside, so there's overlap. I was thinking of mounting the roller shade inside of an inconspicuous box mounted at the top of each window so I can achieve an overlap without having the rollers visible when I don't want them. My game plan is to keep my current mini-blinds and use the rollers simply to black out the room for sleeping (who puts a master bedroom facing east???? My builder did!). Am I nuts?