I stopped by an Apple store today after work and asked the employee manning the line for people to pick up their reservation if they had any pluses in stock ( i knew they wouldn't but had to ask) of course he said no but that almost every Apple store refreshes their stock at around 11pm and you should check apple.com around that time to try and snag a plus model.
I have been trying this for 3 days but never had an approximate time,
take this all with a grain of salt though just passing along some info.
11pm pst? I'm in Chicago. I got lucky on Saturday 3am cst with pluses but for the silver one.