In reality, on a downline, drag equals aircraft weight. On an upline it is less, but it is significant... much more than 3 lbs. That's why it takes a 2:1 thrust to weight to get good IMAC performance... the little extra pulls you through snaps and other higher drag maneuvers.

Good point though... the ratios do work out so that you should have a greater percentage of excess power if you include drag at speed.