Upvote:5
Haven't been on the Philippine Airline version of the 777-300er, but have been on several others.
The double seats in the back are standard seats, no smaller. Because the cabin gets narrower, they can't put nine seats, so switch to 7 in the last couple of rows.
There are some drawbacks. First the seats don't line up with the ones in front, so you may not have as much leg room to stretch out, since the space under the seat in front might not be lined up with your seat.
They are back by the galley and bathrooms so tend to have a lot of traffic and loitering.
And finally they are in the back, so it will take a while after landing before you can disembark, of course this could be positive as well, since the bags take forever to be unloaded anyway.
Personally I would get further forward and just not worry about the row mate. If you can pre-select your seats, you might find a row without anyone, then choose the aisle and the window, leaving the middle empty. If the plane is not full, there is a chance they will not assign anyone to the middle seat. And if they do, likely that person won't mind switching for either the aisle or window so you can be side by side.