port side
I've had good luck with both of mine on the port side forward in a mounted box. I use a remote to control it from the cockpit, when I'm siting on the starboard side it's aimed at the radio, when I'm on the port side I aim it at the window. The tinted windows reflect the beam well.
The picture is of the stereo in Last Penny it mounts behind the bulkhead, on LoKi the stereo was mounted forward of the bulkhead. Seems to work well for us.
One thing for sure wouldn't have a stereo without the remote.