Hi Bob,
Got mine from Bath road motorcycles, Bristol. Nice people there.
Regarding OFF,
I think it would restrict forward/backward and lateral flexion, as well as restricting head plant crunching - the helmet meets the brace and spreads the load to chest/back.
The problem is that your head plus helmet weighs in at 6-7Kg. In an accident, physics takes over and the body may stop and the head not, or visa versa. Any thought one might control these forces is wishful thinking. That is a lot of flexion forces on the neck. It only takes 2KG of force to break one's neck.
The science of the neck brace has been worked out well. I don't think Leatt is actually in it for the money.
There is an interesting aside in US motor racing where the helmets and safety cages were excellent, but the drivers would hit the concrete barrier with such deceleration forces that they would be pithed (essentially hang themselves) and die.
They developed the head restraint which attaches the helmet to a neck brace with 2 small springs - all the GP drivers wear then now.
One elderly US driver poo pooed the whole idea - and promptly died follwing an accident a couple of months later!!
simon