MonarchMan my understanding of the policy was that the Armrest is used as the definitive guide - its not often (ever? not that I have seen anyway) that a tall/muscular person would have difficulty lowering the armrest.
It does get a bit squishy if you have, for example, a footy team onboard and all the lads are fairly big guys. Same as with any "persons of size", we do what we can to help make them more comfortable, but I still don't believe that any one person is entitled to take up more space than what they have paid for.
I myself am quite tall and when I don't have a spare seat next to me it usually makes for a rather uncomfortable flight - but I get what I pay for. I generally try to get an aisle seat if I can, that way at least I have a smidgen of extra room.