I received the OEM extended battery cover on the 21st. The cover fits pretty well. All the buttons work. Today I finally received the extended battery from Hong Kong. It took 2 weeks. The first thing I did was the obvious, place the aftermarket extended battery in the phone and put on the OEM extended battery cover on. Sad to report that it doesn't fit. The after market extended battery is too thick. It missed it by about 1.5mm.
The aftermarket battery is twice as thick as the OEM. i'v opened an extended battery before. Inside are 2 normal sized battery stacked. So I'm imagine this one is the same. The fact that the OEM extended battery is rated at 2150mah and is thinner than the aftermarket dual cell extended battery lead me to believe that the OEM extended battery is a supersized single cell battery. No other aftermarket extended battery will fit the OEM extended battery cover.
The aftermarket extended battery cover is about 2mm thicker than the OEM extended battery cover. When I installed the aftermarket battery cover for the first time, the vol down is pushed in. up on initial boot, it placed the phone into bootloader. I had to take the cover out and reseat the vol control rocker button. Afterwards everything worked fine.