SplitPane under header while still using SideMenu

I got a blog posting notice about SplitPane so I thought I would revisit an unanswered question.

How does one implement a split pane under a main header while maintaining the SideMenu functionality?
This can be achieved with CSS but attempts to do this with the new SplitPane have not worked. Often either the SideMenu contents or the main pane contents are un-clickable.

This is intended to be used on phones and in browsers.
Is this an option or should I stick with CSS to achieve this?

The question was partially answered here but did not implement the SideMenu and some items were not clickable.