Did you ever try verifying a car title at the DMV?

$70 for a box that holds a box? Bold move but honestly if it saves you 20 minutes of watching Dave dig for that one overlay tile while everyone slowly loses the will to live, sounds like money well spent. My group still uses the plastic bag method and we spend half the night asking who took the wound tokens.

Did you try the soapy water trick on the sender flange itself? I fought a 182 last winter with the same ghost leak and what finally got me was wrapping the whole sender base in paper towels then taping a sandwich bag over it. Let it sit overnight with fuel in the tank and a full load on the wing. Next morning the bag was foggy and the towel had one wet spot right at the gasket, nowhere near the fitting I'd been staring at for two days. After that I started hitting every suspect joint with kid's bubble solution before I even pull a panel. Bubbles show a weep under pressure way faster than my eyes ever will.