Just thought I'd report that I was getting an unusually low number of aircraft seen + range... I decided to forgo the short 6" USB A to A that I was using between my Pi and my SDR dongle, and when I plugged the dongle in directly into the Pi, my aircraft count quadrupled!
I'm still toying around with gain settings, antenna type and placement, to see if there are other factors, but man that USB cable apparently was wrecking my setup.