My unit has 128MB or RAM built-in. It then has ONE slot for additional memory, and the most that can be is 512MB - which it just happens to have!
So my particular computer has 640MB of total RAM in it - more than enough for RTD Explorer, but the more the merrier for use as entertainment system.
One downside of the Geo Metro, is that it has a small dashboard - there really isn't a lot of space to build in custom computers and things.
My car has driver AND passenger airbags. One guy suggested removing the passenger airbag, and building the computer into the dash there. I don't think that would be ideal, and it would be a poor viewing angle. Also, I don't know what my insurance agent would say about removing an airbag....
I think the tablet would be best on some sort of a swivel mount, so the viewing angle could be adjusted, but it could still be out of the way when I am driving with a passenger.