The problem really lies that there is zero evidence (apart from anecdotal) as to whether it is better or worse. That means there is as much a chance it will make it worse as better. Those odds do not appeal to me.
The CIK-FIA are the only organisation who would bother to test these, they’ve been around a while and they haven’t decided testing is needed.
This topic has done the rounds on many a message board. The foam next braces are generally deemed a hazard as they prevent the neck from flexing anywhere but the top of the neck.
In 2013, at the Watkins Lecture at the Autosport Show, Andy Mellor, the Technical Advisor for the FIA Safety Institute said that regarding HANS type devices for karting that the jury is still out on these and they are struggling to get answers as to whether they actually do aid safety or not and are currently devising a new test to help with a decision, which they still haven’t.
Anyway as with anything that isn’t accredited I believe it should be down to choice given the information available. I’m not going to sit here and tell you what to do, but I do have a problem with a sanctioning body telling me I have to do it with zero evidence. Fortunately that only happened once (in France).