Never heard of this before....could you explain a little more and tell us HOW you fixed this issue?
Sorry about that, I was using my phone and I hate entering long messages on that little virtual keyboard.
So, I wanted to install tower speakers and of course I wanted them spaced evenly. To get the spacing, I drank a beer, then I found the center of the tower and measured outwards from center. I put the speakers up, spaced evenly and drank another couple of beers admiring my handiwork, then I stepped back outside the boat to see how the placement looked and if I liked it. Something looked a bit off; called my wife over and had my artist daughter come outside to see if they both saw it the way I was. I didn't tell them anything, just asked them to look and tell me what they thought. They both agreed that the speakers didn't look evenly spaced over the boat, port side looked too close to center. Damn, it's not the beer throwing my vision off. Ok, so I go up and re-measure, all is good, measurements to center of the tower are spot on, checked the angles of the speakers with a digital protractor that I use for chassis and rollcages, both speakers are hanging at precisely the same angle. Ok, sumtingwong here. I moved the port speaker out until they said it looked even with the other one and then measured back to center.....3 1/2" difference, but when I looked from their perspective, the speakers looked evenly spaced in relation to the boat. I checked to see if they had been drinking anything, but they said they hadn't. I said maybe they should.....
So next step is to check where the center of the tower is in relation to the center of the boat. I dropped a plumb-bob from the tower center point, and after making sure the windshield was reasonably well-centered on the boat, used the distance between the windshield frames on the port and the starboard side windows to reference boat centerline. Sure enough, the tower centerline was off of the boat centerline by about 3.5" to port. Fix was relatively easy on this one, I simply loosened up all 4 tower mounting bolts under the gunwale and shifted the whole tower starboard to center it up. Movement at the tower mounts was actually minimal and translated into a fair amount of movement out at the center. Side note challenge: Loosen and tighten your tower bolts (acutally studs with nuts) without ever looking up inside your gunwales.
Put the speakers back in their originally measured location and looked again from outside the boat......voila! Perfection!.....or close enough. Time for another beer.