You should be setting it to 800 (the horizontal resolution of the Evo's screen) and checking the "keep aspect ratio" button. Will do a more detailed writeup once we have the phone and can test a couple of bitrates.
If you want a good jumping off spot to convert now, check the Iphone preset and change the horizontal resolution to 800 and check the "keep aspect ratio" button. Make sure your audio track is set to english (or whichever language you're looking for), and convert it. You shouldn't need to change any other settings.
Once we have the phone, we'll be able to mess with the bitrate and other settings to see if we can get a smaller file size. Going from an HD source, using the settings I listed above your file should be between a gig and 2.5gig.