Connecing my newPGXL to my flex

If you're just using these 2 Flex equipment in a stand-alone configuration (and not to the internet), then just connect them to each other via ethernet cable. Otherwise, I'd recommend that you plug each of your networked equipment into an ethernet switch. In an all-Flex system, you'd only need other rear panel interconnect cables for auxillary equipment that's not designed for ethernet connection with Flex equipment. Review the Flex "Dream Station" document.

Your 8400M RF output connects to PGXL RF input. The HF-Auto would go between the PGXL RF output and the your Antenna. Ethernet cable from Router would go to an Ethernet Switch (example: Port-1). Ethernet cable from 8400M goes to same ethernet switch (example: Port-2). Ethernet cable from PGXL goes to same ethernet switch (example: Port-3). You may want to look at using W1TR's HF-Auto control software, if you're not already using it, but since I use a Flex TGXL tuner, I can't help you with the HF-Auto.

Sorry, I forgot to mention that there are 2 DDUtil versions (v3 & v4). I believe you need to use v4 with a Flex Radio.