So I noticed in the demo they gave for the Roadster that the frunk and trunk were unaccessible. That leads me to believe that that is where they shoved all the extra batteries needed to get the roadster up to 620 miles of range. But that of course will not work for the production version, so they will need to put the extra batteries somewhere else. Now a lot of people here have hypothesized that they will simply double stack the floor mounted battery pack. Unfortunately, this seems like a bad idea as it would lead to significantly reduced overhead space in the cabin for the driver and his/her occupants. However, there is another battery placement option I have not seen discussed here. The additional batteries could occupy the same space as where a traditional ice car's drive shaft would have been; and hidden under the center console. The remaining batteries can then be hidden under slimmer modified versions of the front and rear seats of the car. See Below. In fact I like this idea so much why not, after the Roadster is finished, add it to Tesla's other offerings. Have a "range extending" checkbox option for a price somewhere between 35,000 - 50,000 which would essentially double the size of any car battery. How great would it be to get the Model X, Model S or the Model 3 in a 600 mi version. A version nearly imperceptible from the non range extending version.