I measured the thickness of the wall of my helmet at what appeared to be the point of primary impact, on the right in this photo. It was about 8mm compared to 15mm at the same spot on the other side of the helmet.
The area of crushed foam covers a pretty large area, so it absorbed a huge amount of energy. Certainly more than my head could have! My Bell Sweep did its job. The bracelets are just souvenirs from my ride.
I'll try to get back to more general topics, but I've been admittedly self-absorbed over the last few days.