My Adventure Leatt brace arrived today. My wife took some piccies tonight to give you an idea of the positioning. Apologies for the ugly model but that's the best I coudl do
First let me say that the restriction you expect from this brace is not at all as such. There is NO and I repeat NO restriction in sideways movement. It is important to understand what the purpose of this thing is and how it actually works.
According to the manual, the GPX is designed to prevent a whole range of injuries with names in medical terminology, which I have transcribed into English:
Hyperflexion, Hyperextension and Lateral Hyperflexion: Extreme forward, backward and sideways movements of the head.
Axial Loading: Compression of the spine. An extreme example is jet pilots ejecting from their planes and coming out a few centimeters shorter.
Posterior Hypertranslation: I’m no neurosurgeon but from what I gather this basically means having the head travel backwards at high speed to somewhere it’s not usually supposed. It plays a key part in whiplash injuries.
Front View with head in normal position, note the space between my chin and brace
Front view with my chin down as much as I can down on the brace, it is not a great distance and this is where you will understand the principal of this brace
Rear View of the brace with head in normal position
Rear View with my head fully tilted back, the movement is not that much but enough not to annoy you. I actually think you can become a bit lazy by resting your head on your back
You can adjust the rear stop into several degrees forward or back to suit
Sideways movement certainly no restiction and this is where I think most people's concern would be. I turned my head much more than I would normally do a life saver.
I also tried the brace with a buff and scarf and you can adjust to comfort. It actually does not sit tight and I can see no reason why this should not be 2nd nature by the end of tomorrow for me. It lies on top of your shoulders basically and they provide shorter and longer clips depending on the width of your chest and shoulders.
Bought mine at MX1 for £163 delivered and more than happy to meet up in the city (central London) should you want to view and try it on. Personally I think it is just that extra peace of mind but certainly a choice and decision you should make based on your own perceptions. Been riding for over 20 years, wish this was developed when I started as it certainly would of made differences in all the people I read, saw and heard off over the years breaking their necks in silly bike accidents ending up either dead or paralised.
Hope the above helps and take it easy out there
I already have by helmet, back armour and Aerostich over trousers, plus my boots if I'm going somewhere nice. I really don't think I'm gonna be able to fit the neck brace in the as well...
As with all things pretty sure you either get on with it or you don't. Yet another thing to carry around but willing too do that if it gives another level of safety. Afterall if a truck runs over me no neckbrace is going to help but there is always that small silly offs that you pay dearest for in life 
