Odd that the closest vents are the poorest; it's usually the other way around. You might want to drop the inside cover from the AC and look at the actual openings from the cold air plenum into the ducts. They are often very small. You have to cut out some foam to enlarge the opening.
1988 Coleman Sequoia - popup (1987-2009)
2012 Roo19 - hybid (2012-2015)
2016 Mini Lite 2503S - tt (2015 - ???)
2011 Traverse LT, 3.6L, FWD
2009 Silverado Ext Cab, 5.3L, 4x4, 3.73
2016 Silverado 2500HD Dbl Cab, 6.0L 4x4, 4.10