Yesterday was cold but clear, and feeling a bit stir crazy after being inside for the last week, I decided to head out again. I added some more pressure to the fat tires (how much? I don't know, since my floor pump doesn't seem to read below about 20 psi or so), and headed towards Avery Park. The added air pressure really helped the bike move along--it no longer felt like I was dragging an anchor behind me.
Someone helpful person had packed down a path through the park:
The fat tires did fine on this packed surface, of course, but so did my regular tires when I came back and rode it on the ERB (why not on the Razzo? It's been sold). If I diverged from the packed line, progress quickly ground to a halt in the ~7" deep powder on the sides.