Most good, or lets say professional linemakers have a formula, or at least an automatic number, they can use in just about any situation. As far as trying to use a number that covers one sided action on the game itself, I believe that would be foolish. The 2nd half is a separate bet, and considered a separate chart. Maybe some of the real linesmen who post here will shed some light on the subject. I am far from an expert.
wil.