Food for thought with the HANS device, using it without a roll cage COULD be bad news in the case of a roll over situation ( unlikely but it is Motorsport)
The HANS will restrain your head and neck just fine but if your on the lid and the roof has crumbed in, you could potentially be caught in a situation where your head is stuck in place and could cause more injuries.

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2016 Subaru Outback - Work Wagon
350NM of CVT Goodness
Pit Crew, shit talker.