Use the sticky pads for guidance only, ALWAYS SCREW motion sensors in using the holes provided. You can never trust a slightly heavy object especially a motion sensor tripping an alarm if the sticky tape undoes itself, or on a hot day.
Picks up motion fine on mid setting, it won't pick up motion every second this is to save battery life. There are no concerns regarding lack of motion as mentioned by others, the 2nd gen picks up motion every 5 to 10 seconds on purpose.