Unity iOS App Size

Hi guys! I want to know what is the Smallest possible Unity iOS app size. If I build an Empty Scene Project(just one main camera or without - please specify) and build wth Xcode.
I need to know this to help me decide wether I must use Unity or not for my app - as the final size matters.
What must I do to ensure these?

according to the unity manual the smallest app size in iOS, is 24 mb, 12mb if using code stripping.