Thanks to all for the responses. I have a Tanis heater for the oil,
but just was wondering if an air-flow heater might be useful here. I'm
in Montana, and temps well below 0 degree F are not uncommon in the
winter. An airflow heater can warm up the engine and the cockpit for
the sake of the avionics. As for putting together something myself I'm
reminded of the old Groucho Marx joke about belonging to any private
clubs: "I wouldn't join any club that would have me as a member."