Weird edge case issue with DrawerGestureModePanning

Our case is we have a central view, that uses a custom navigation bar, and not a standard navigation controller. So by appearances, there looks to be a navigation bar on screen.

Our central view has a drawing/annotating element, so needs to listen to touch events, which the center panning mode is eating up.

If I set the open/close drawer mask to MMOpenDrawerGestureModePanningNavigationBar, the center basically goes dead. 

There is a redesign of the center controller's UI underway, but any alternatives in the meantime?