Hi Rick,
That’s an ADEM 2 HeadRest. Unfortunately Don doesn’t appear to make them anymore as ADEMHR.com is gone. It’s modified with a custom Ventist Pad. It’s not overly fancy, a bracket, a bent piece of mental and a plate. I don’t recall if that’s documented in the old V20 docs.
I’ll add that to the list for the V20C build photo journal.
…. (Don’t get too excite the saving up for that just started and switching to through axle wheels, AXS and the frame allone means that will be a year out minimum. Maybe it’s time for patreon project for me to create the optimal build, complete with parts list and detailed instructions…..