I highly recommend picking up a soft measuring tape if you're going to be adjusting the screen to exact proportions. These are commonly used by two groups of people--tailors and doctors. If you've ever had your waist measured, you've seen this type of tape. I've been using one of these tapes for screen adjustments for almost a decade now and have found it one of the most valuable tools I've ever picked up for compact Mac work, right up there with a long-shafted T-15.