Got my passport stamped at Charlotte office today (Friday).
Although the approval letter says they only work on pp stamp Tue, Wed & Thur, nobody asked any quetion why I showed up on Friday. I believe they put the wrong office hour info on the approval letter.
Here is some more detailed info.
Got there by 6:45 AM and there were ~30 people waiting in line
The guard let people in at 7:30 (no food/drink allowed, even just bottle water)
The officer at front desk issues token based on what you need to do
my numnber was called at ~8:45AM
get finger print and turn in all docs
waited another 30 mins for security check
Got out at ~9:15 AM
Good luck to everyone who is waiting for apporval.