Honestly, I've never seen a boat with instruments (other than an autopilot with a plastic cover, and yes, it was a PITA to get to much of the time!)
mounted where you're planning to have them done. I can't imagine having to crane my head or neck around unless you're mounting port and starboard repeaters, and even then, you can't see them downwind if you're driving, not to mention the cost. And this is all before you have other people banging into them, in the way, etc. On the other hand, I've seen a lot of boats use an instrument pod/box/etc... mounted forward of the companionway built into a spray hood.