It never happens on the left side when the left tank is full. Why the difference?
Give it time -- it will
This happens on certified aircraft as well (Cessna 210, 182, etc.)
If the hangar floor is slightly tilted, or the aircraft is slightly higher on one side due to tire inflation difference, it may not dribble.
The solution is to not fill up the tank to the tippy top -- leave a 1/4" or so between the bottom of the fuel cap flange and the top of the fuel.
I initially, the fuel level was about 1 inch below the top of the tank when I filled it. Now it is about 2-3 inches down. That is the amount of fuel that has leaked on the hangar floor in the past month during the heating and cooling each day.
It looks like I am going to be making a tool to tighten that nut and hopefully fix the leak.
Shouldn't need a tool for a -7. Pretty sure you can reach in there through the fuel sender cover plate.