So my CS arrived today and I've been closely following everyone's mounting ideas. My solution involved planing down a piece of scrap wood to 5/16", cutting it in the shape of a phone and tracing the battery shape onto the wood for the cut out. You have to be very careful with the cut and sneak up on the lines to get a snug fit.
Once it fits nicely however, it's golden. You can shake it upside down and it won't fall out. No screws, no velcro, no metal of any kind to cause interference. Sets up in seconds and best of all, it's free! I made another one out of 3/4" wood for my P3P. Paint is still dryng on that one, but I'll post pics here later when I set it up.