pretty annoyed at whoever installed the unit, overlooking that seems amateur - it is an obvious necessary setting. Now I just think of all the years of wasted money on heating/cooling when it could have been moving more air over same time frame.
I finally figured this out, and wanted to let others know in case they encounter such issues. The air handler (Rheem RHLLHM6024JA) has an adjustable blower motor, controlled by wire taps. According to the specs (conveniently written on the outside of the air handler unit), the motor should be tap...