measuring from the floor to the bottom of the 2x12's, the right side is 86", the left side is 85 3/4" and the middle is 85 1/2". i'm not sure how straight these things normally are, and how long if it all it would take it to sag over time. i just don't want the house to come down on me.
other than the center post, is a garage with an 16' door normally built different? would putting another row of 2x10's or whatever above the door help any? my truck will barely squeeze in a 8' door, so i'm really trying to avoid that.