I’m not Danny King but I liked his idea of circulating warm air to the back.
Since I bought a stainless heater box, the aluminum one was repurposed into a plenum to attach a scat tube. The “Y” tube (from ACS) with a valve can shut off the NACA vent and only heated air will come out the panel. Two Bowden cables will be needed. One for the Y and one for the heater box. Air flow to the panel vent can be fresh, combination of cold and heat, or just heat.
The plenum has enough opening to provide equal amounts of hot air to the front and the vent. There is a panel on the side that can be replaced with a larger to small size depending of real world results to increase/decrease the air volume up front.
I still have to adjust the scat tube lengths but the picture was the initial run.
As a side note, the Stein large air vent has a bulge on the tube the scat hose connects to. It had to be cut off to get the scat tube to slide on.