After reviewing both the manuals for the fuel probe and for the Dynon, I have the gremlins at bay. A few points: tri gear Sonex sitting level are hard pressed to take more than about 14 gallons of fuel. To get 16 in I had to put a chick under the nose wheel. The dip tube for manually checking the fuel level didn't work very well, and is going to be replaced with a wood dowel painted flat black. The actual fuel calibration routine in the Dynon SkyView is not like the manual - you tell it how big the tank is and it will tell you the size of the Pours.. For the last Pour in the sequence you press Add, then Full.

The key was calibrating the Princeton/RED box to zero before starting in with the Dynon calibration.