For the archives:  anyone interested in cabin heat add on. Here's a few pics from my KF5  It has the cabin heat option from kitfox Pic below shows heater core with 2 fans on top, inlet and outlet lines.  Valve that shuts off coolant flow. This is cockpit side of firewall, above rudder pedals,  heater is behind the instrument panel.  It has pvc plumbing that runs hot air up to defrost (white tube in pic) and another aimed towards feet.