Hey FC,
kGADSizeBanner is a 320x50 ad that works in both portrait and landscape. On landscape though, the 320 width doesn't take up the full screen.
This is the motivation for the kGADSizeSmartBanner{Portrait|Landscape} constants. These constants take up the full width of the screen. So kGADSizeSmartBannerLandscape would be 480x32 on phones, and this constant should only be used on landscape. kGADSizeSmartBannerPortrait will be 320x50 on portrait on phones, but should only be used for portrait. On tablets, kGADSizeSmartBannerPortrait should be 768x90 in portrait, and kGADSizeSmartBannerLandscape should be 1024x90 in landscape.
I'm not sure if you're trying to hack together a 320x32, but we don't support that format. In landscape, I'd recommend the 480x32 smart banner, or just the 320x50 regular banner, depending on what fits your needs.
Cheers,
Eric