Here is some construction information. Maybe it will help others who are contemplating a similar project.
The SPG plate will attach to the shack wall, right over the existing panelboard. A backing of 3/4 inch plywood will sit behind the copper panel.
The SPG panel itself, after lots of work.
Here are a few details. The custom cut copper sheet is 15" x 20" x .0647" Copper 110 = 16 ga. or 48 oz, supplied by OnlineMetals.com. They provide great service. You can see a number of 1/4-20 wingnut connections for miscellaneous ground strap connections. There is also a clamp for 1.5" copper strap, for eventual connection to a new external earth connection. The Polyphaser PLDO and ICE 348 devices are described in earlier posts below. The Hyperlink DSL protection is also visible, along with a number of PolyPhaser coax surge devices. Various antenna switches surround the panel, but are not part of the grounding system.
Tabletop Ground Bus
Using another copper sheet, 6" x 48" x .0647", we constructed a tabletop "ground distribution system" to provide a well-defined reference for the radio desk.
One connection bonds the ground bus to the metal office desk. Another connection goes a couple of feet across to the SPG plate on the wall. One-inch tinned braid is convenient for these connections.