I decided that the AN fitting in which I mounted the Grand Rapids OAT probe looked a bit, well, squared-off and un-aerodynamic. I ground the edges off a bit, and it looks better now. It'll look even better after it gets painted to match the airplane someday. (I'll leave the white probe itself unpainted.)
Time to mount the thing. I located and drilled out a 9/16" hole for the probe in the bottom of the right wing, just aft of the middle access panel. I primed the hole and installed the probe, then routed the wires under the wiring conduit, along the bottom edge of the large, nearby lightening hole, and through the ribs (through the small, pre-existing wiring holes). Finally, I secured the wires in several places with zip-ties.