Originally Posted by
Blackheathflyer
Just a thought, but how do you suggest measuring A on a consistent basis - perhaps using the clips on the tray tables?
Centrers can be difficult to measure, so a trick I learned when working in a machine shop was to measure edge to edge. The distance is a the same (especially when measuring hole centre-to-centre distances drilled in a piece of steel) Say the left edge of seat A to the left edge of seat B.
Takes the guesswork out of exactly where the mid point is and should be easy to get repeatable results from many people measuring.