How do I support portrait and landscape?

I am sure I am missing something simple here.

I am trying to setup two layouts that use the same event sheet.

At the start of layout I'll check if its on a mobile device and send the user to a portrait layout. If not it uses the landscape layout.

My issue is that I can only work out how to setup the project window size that will either cut off the portrait. Cut off the landscape or leave it square.