I'm not bothered about the meal - the problem is being a mathematician! You have a matrix of points (the seats) and we can assume a continuous line joining them (the meal allocation). If we consider the set of all possible lines that go to 'adjacent' points and assume each is equally likely - even though they won't be in real life - is it possible to pick a point that maximises the probability you are at most X% of the distance from the start of a randomly chosen line from the set for various X?

That's the interesting problem, and the sort of thing I ponder while in an aircraft unable to anything more productive.

Now as I say, the actual paths are probably fairly limited and not all equally likely -   seats ABC going 'up the aisle' and then all the seats DEF 'coming back', for example, seems quite a likely one whereas all A in increasing rows, then all B seats in decreasing , then all C increasing ... is pretty unlikely.