Is it possible to disable the soft touch keys without an app/mod?

I'd like to disable the touch keys that are taking up display real estate and have my Nexus 7 2013 be in permanent immersive mode or full screen mode. I'd like to use Pie Control instead to navigate my screen. Is it possible to disable them? I tried apps like Hide Soft Touch controls and they can be flaky switching back & forth between full screen and non-immersive mode. Is there a hack that can do this that doesn't affect system stability?