I recently fitted a 3800mAh battery which included a new back cover to cope with the extra thickness of the battery. All up it added 5.4mm to the phone thickness, so it no longer fitted my first cradle design.
I also had to dispose of my soft gell cover, and fitted a bumper cover instead through which the new back cover fits extremely well.
The new design retains the charging and antenna, but now allows both a standard nexus phone (with bumper or full gell cover) and an extended battery cover (with bumper) to slide down into it and be charged if you have a USB charge adaptor available.
Additionally, I removed the "by Shaughan" motive as I wondered if that put some people off from printing a cradle for themselves.
Once printed, you have the option of purchasing a micro USB car charging cable for it. Insert the micro USB cable through the square hole at the base and slide the phone down to meet it and then push the phone all the way till it seats. Carefully then spot some super glue around the micro USB plug and the square hole to locate it in the correct position. Once dry, carefully withdraw the phone. You can now add more glue or carefully fill any void with silastic or aradite or something that locates the plug permanently. Sliding the phone in should now line it up to meet the micro USB plug every time.
The four holes on the flat back of the holder are for a cheap Samsung car holder I purchased off eBay. It has a suction cup for the windsceen, or alternatively a vent mount. They are about $14. The part that meets my phone holder is a rectangle with four tangs that fit into the back of my holder, and pushed sideways to lock in very positively.
The larger recess and thin channel in the back are for a antenna coil I also found on eBay. Its postioned up against the back of the phone and allows it to use an exterior car antenna. The channel allows the cable to exit from under the mount.