Increase bottom layout length/inset/padding

Question

1. Subclass UITabBarController
2. Hide/remove original tab bar
3. Put custom view to bottom of the UITabBarController view
4. UITabBarController -> UIViewController -> UIScrollView (pinned to superview all edges, not layout, and set adjusts scroll view insets on vc to true)

Expected: UIScrollView's content is fully visible when I scroll to bottom of the scroll view

Actual: No inset applied and scrollview's content goes under my custom view.

As for iOS 11, additionalSafeAreaInsets is working as needed. But what can I do for iOS 10 & 9?

Overriding bottomLayoutGuide never called. Setting view.layoutMargins did not help