RE: Ricky Battery
With a little bit of rotary tool work, you can fit a flat non-plastic-cased LiPo pack. The thinner the pack, the better. The LiPo packs shaped like a six-cell side-by-side pack won't fit without serious Dremel work because the battery mount is molded to the shape of a six-cell stick (shotgun) pack.
Use Deans Ultra Plug or the new Traxxas connectors to handle the current. Also, be aware that the stock all-in-one Rx/ESC unit doesn't have low-voltage cutoff (you probably figured that one out), so bring it in as soon as it starts to slow down.
Oh, and I believe that a 19-turn will work with the stock electronics, at least for a while.