I just got some new production start dates for the next few 787s (up to L/N 53). L/N 50 was the latest 787 to start final assembly (started on Oct. 27th). Here are the following final assembly start dates:
L/N 51 - Nov. 10 (14 days)
L/N 52 - Nov. 22 (12 days)
L/N 53 - Dec. 6 (14 days but take back on day for the Thanksgiving Holiday, 13 days)
In order to be producing at a 2.5 aircraft rate, Boeing needs to start final assembly on a new 787 every 12 days (excluding holidays and assuming a 30 day month). It looks like they're trying to get there but I was expecting L/N 51 to start final asembly a couple of days sooner.