After my trip to Perth I decided to tidy up the office a bit, by remounting my Spot Messenger and my handheld CB radio.
The CB mount is now via a MCL clutch reservoir mount, which replaces my original cover. This is a neater option than the previous RAM ball mount that screws onto the top of the original reservoir cover.
My second improvement was to fabricate a mounting plate for the RAM Spot Messenger holder, from some sheet stainless steel. It's a much more elegant solution than the complex RAM ball gadget that I was using before.