I mounted mine at the top of the half-bulkhead over the port quarter-berth, because access was good for me and the wiring runs were better from there. It's close to the fuse-panel and the batteries, and Bossa Nova had a couple of access-plates in the headliner that I was able to remove for cable-runs. And even though I sleep in that quarter-berth, it's high enough not to be at all in the way.
The computer box on the X-5 is supposed to be mounted athwartships, so that it stays vertical while the boat is heeling. I don't know about the S-1, but it couldn't hurt to put its computer box in the same place.
My display-unit is on the seat-back to port of my pedestal. It's in easy reach from the helm, but far enough back that passengers who sit there don't have enough foot room to be comfortable. (Since I'm usually single-handing, putting the controls there was not a problem to anyone who might be sitting there.)