I followed the instructions at "Using Composite Video Output" and they work fine, but the aspect ratio is still 16:9 stretched to a 4:3 display.
I also followed the instructions at "Setting up an Apple TV with a Standard Def TV" and they work fine including the 4:3 aspect ratio, but if the Apple TV is ever restarted it goes back to the screen where you have to select a display resolution. On that screen, 853x480i isn't an option and you have to perform the cable trick again to get 4:3 back.
Is there any way for aTV Flash to permanently set the resolution? It seems like there's a start towards this on http://wiki.awkwardtv.org/wiki/Composite and http://wiki.awkwardtv.org/wiki/Talk:Composite but it all seems for older Apple TV OSes. Anyone got this working on 3.0.2?