Interesting, I've never heard that complaint with the adjustable version. How bulky of clothing are you talking? I never wear more then a shell and a base layer and the pins that come with the leatt can easily adjust for it. I wear mine with and without a chest protector for moto and it does not restrict me in any way on the bike, off the bike it can but that doesn't matter.
I boondock and have considered wearing mine for if the sled were to roll onto me, I could see some situations where it could really bend you the wrong way. I've guys wearing the around here, even on powder days, I mean why not?
I actually had a Astar brace for a while but returned it. The Leatt is much higher quality and adjustable, the Astar is not adjustable. The Astar brace is just not as nice as the Leatt IMO. I had a medium Astar. There sizing chart I was on the border of M/L so I down sized. The thing was huge, I could lift it off my head with it latched, and I wear size XL helmets so it's not like I have a small head. My main concern with the Astar was that it did not come contact with the rear of my helmet when I tilted my head back, if I were to unstrap my helmet and push it back it would hit my back not the brace, so i do not see how it could prevent hyperextension of my neck in that direction, which from what I've gathered is the most damaging. My Leatt on the other hand comes in contact with my helmet just as I reach the limit of my necks natural extension.
just my .2 cents, hopefully some of you can find it helpfull.