The issues I had with not picking up aircraft were entirely my fault. The little 1/4-wave vertical antenna I made for this was inside the sunroom, hanging on the Venetian blinds, and I had doubts if enough of the 1090MHz signal would get inside. The window screens are aluminum (SHIELDING!), and the fiberglass insulation in the walls and ceilings is also aluminum foil backed (MORE SHIELDING!!), but since I was receiving some aircraft, I should be able to decode them.
As soon as I moved the antenna outside of my "Screen Room", I went from getting A few aircraft displayed to having a screen full of them, and now the "Show Tracks" works, too.
MUCH better than this:
Which gave me this:
Since I'm running this on a little RaspberryPi mini/micro/nano computer, I went and installed the official "PiAware" software from FlightAware, which got rid of the "For Development Purposes Only" map overlay, and has more adjustments to select.
Now I just have to move the little antenna to a mast, and tidy up the cabling a bit.