Just a minor note about row 5 on the DC9:

It is a 2-3 configuration--

On the left (port) side of the plane, the rows are 5A and 5B; these are the usually designated handicapped seats;

On the right (starboard) side of the plane, the rows are 5E and 5F; these are usually open to any elites;

There is no 5D, hence the unlimited leg space for those in 6D.