Seems like for a week now I have been working on the cowl, sanding and sanding, etc. I finally got tired of sanding and decided to finally attach the 90-degree TNC connector required for the Garmin Ga36 antenna used for the ADS-B Out. There is a $6 connector, and a $52 connector. Near as I can tell the difference is the expensive connector uses a crimped pin, where the cheap connector is soldered.
So, went about trimming the RG400 cable for the TNC connector, cutting away the outer and inner shield, and shield grounding as required. Inserted the connector on to the trimmed RG400, then soldered the interior wire to the post of the connector. This was not as quite as difficult as I had imagined.