From reading through this thread, I guess there is no answer to this question. But, wondering if anyone knows how main cabin extra is going to work on this 77W. For JFK to Heathrow in late June. Rows 16-19 are blocked and I'm assuming these will be Premium Economy. As others have mentioned, there are three center rows of MCE in the back of the plane. Looking at the map, how can these have extra leg rooms, but, not the window seats on either side? The site that show seat configurations, shows this configuration. But, it's not updated for the premium economy and the change in the MCE seats.

And here is the map: