I officiated at a stage rally last weekend. This year, most people in motor sport now have to wear and use a HANS device or similar (FHR), and this was the first event I had been on where that has been true. It became painfully obvious that many drivers and co-drivers were in the same boat.
My Rescue crew leader first noticed that a co-driver's helmet strap was not attached to his HANS, so we had a look at the next car's crew - and their straps were undone too! And another, and another, until we asked the Stage Commander to help, as we were holding the stage up. We were on Stage 3, not the very first, and by the time the field had gone through, we had found at least 20% of the crews weren't using their FHRs correctly. I'm sure that this was due to inexperience, as this was first rally of the year for most of them.
Drivers of 'historic' cars are not obliged to wear a HANS, pre-1968 for rallies, pre-1977 for circuits, Sprints and Hill Climbs (
https://www.msauk.or...fhrguidance.pdf) but even so, I would urge you to do so. And I would be even more eager that you wear it properly! Get someone to check it for you, before you get in, and then after you are seated, at least for your first event!
John