Once you scroll down on CupertinoSliverNavigationBar the middle widget automatically appears -- this widget cannot be customized while simultaneously having a customized largeTitle. If you try to use a custom middle widget it will appear even while the largeTitle is active in its regular state. There's really no option to customize the middle state of the largeTitle.

Can't customize:

Can customize:

Right now both have to change together. Ideally you could set a different font weight, or even a different widget when the large title is gone.