Since the ground connection to the bulkhead N-connectors is provided only by the 4 stainless steel screws because of the plastic enclosure I wanted to make sure that the ground connection is very good. I used 4 pieces of de-soldering braid to create a "bridge" between the screws and then used washers and nuts to attach the "bridge". I also made a connection point for the coaxial by using two ring terminal connectors on each side. Then I "soaked" the braid with solder and soldered the ring terminals to each other too. With this approach, all of the 4 screws are grounding the connector to the braid of the coaxial.