Earth ground to dsub9 shell
It is a good idea to ground DSUB connector shells. See here for a first hand account of what might happen if they are not: What is the &quot;ground strap&quot; on a D-SUB connector for?

A ring crimp connector on the jack screws that connects to a wire going to the ground bus should work just fine. In fact, I did almost the exact same thing on one of my projects and have had no problems.