Hi,
sorry, but I don't know if there is any iOS fullscreen hack to make that possible...
As note - iOS itself doesn't provide a fullscreen mode, depending on the iOS version and device different hacks were used to get into a fullscreen mode, and even these hacks have limitations.
If you have see a website anywhere that is able to do that, please let me know and I will analyze it and try adding that to krpano as well.
The problem itself appears only on the 'plus' iPhone models. It seems Apple has thought the screen is large enough in this case, so that a kind of fullscreen mode is not needed there

.
Best regards,
Klaus