It sounds like you want to mirror your iPad display onto the tv?
If that is the case then you cannot change the aspect ratio because you are mirroring your 1024x768 screen.
Status board is designed specifically to support a second screen and does not mirror the iPads display.. this is done because the second UIScreen has a size that supports the physical screen.
If you want to optimize your app to support a second screen then check this out: https://developer.apple.com/library/ios/documentation/WindowsViews/Conceptual/WindowAndScreenGuide/UsingExternalDisplay/UsingExternalDisplay.html
Otherwise I'm aftaid you have to live with the black borders..
Think about it, if you tried mirroring your macs monitor onto an external display then this would still be the case