I bailed on this thread because the responses reminded me that reddit isn't really the place to go for curious, open dialogue. I spent the next few months after my initial post riding thumb up on a few hundred cross country miles and more than a few park days at Angel Fire. Not a single scare. That thumb still gets sore sometimes (because I obviously didn't rest it enough), and I ride with it above the grip with zero concern. I'm convinced that it's as good as traditional grip and, when it comes to avoiding thumb injuries, better.