Content size based scrolling inside nested scroll view

I am using Nested Scroll View inside Default controller. The body of nested scroll view may contain stack, other scroll views (custom Scroll view) or normal containers depending what kind of page user is in. In some pages list of items are displayed without tab bar in the app bar. In other cases, there is a tab bar and the body of the nested scroll view contains the corresponding tab view.

App bar in the nested scroll view consists of the extended widget using flexible space bar. When scrolling down the page, the body of the nested scroll view moves up and get behind the app bar.
This view might be okay with list body content but when it comes to other normal contents such as container, items get behind the app bar hiding part of its view. It would even be more useful when the contents are sufficiently viewable in the viewport ( existing page), there exists no scrolling at all.

I implemented SliverOverlapAbsorber and SliverOverlapInjector but it hampers my existing desired UI format. Also, body view is not stable. Ran into min extent issues

Sliver Overlap approach