My 2 cents thoughts:
2001 - Flight testing; First prototype; Initial data gathering
2002 - Flight testing; Second prototype; Advance data collection
2003 - Combat flight / weapons testing; Improved airframe; Initial combat tests
As for the walls, fans could easily mount the DV cam onto a RC helicopter to take the videos. You can hinder them, but there is no stopping of them.
And one rumor has it that: 2004 - WS-15 installed... not sure about the 2002 - weapons testing though.
Big shrimp, Pupu, also says that WS-15 project is going well and there are many J-20's out there.
P.S. For those of you non-Chinese who might be interested: Big Shrimp sounds like 大侠 and 大侠 means sort of a kungfu master, especially a legendary one. So those who enjoys lots of followers/believers (say, on the web forums) are jokingly called 大侠 (in the internet world), hence 大虾(big shrimps).