Is there to small or to big of a magnet strength/size. I wouldn't want to go to big and end up damaging the device. or having issues with the screen.
Why do you need magnets when there is a shortcut for the car mode already in the apps page (Car Home), and Dock Runner is available for home mode in the Android Market? If you must use magnets, check this vid first: http://www.youtube.com/watch?v=PHOijz2fWg8 ...go small. Magnets + sensitive electronics = bad.