Just a follow up and thanks as this thread was very useful to me.
This boat is a 1990 Mac 26S with the Laz and outboard well / transom and I finally settled on the spot in the picture for mounting the RAM trying to minimize the risk of breaking the socket/ plug off while sailing or loading something in the Laz, stepping on the mic, accidentally snagging the cord or losing some seat space. Still a compromise..
The RAM seems to very nicely solve all the problems I had in the first post. The RAM speaker volume is plenty loud to be heard while Im running the outboard. I can almost completely control the radio from the RAM, even turning it on and off. The volume control of the RAM is independent of the radio volume control which is something I was hoping for. The AIS screen on the RAM is small.. but at least without ever actually using it, seems large enough to be useful.
I also mounted the radio in the cabin under a section of the deck that almost certainly has a plywood core. I haven't discovered if the radio has a GPS signal strength screen.. but the GPS seem to work just fine. So, add another data point that the internal GPS antenna is likely adequate for a trailer sailor.
Thanks again! I enjoyed the project and am happy with the results.