I wear the EVS, I was really skeptical at first but i got tired of choking myself out collar after collar. When I first put on the EVS it seemed way to loose and I thought it was to big. But I wore it out practicing in my Shifter. I will say what a difference. The side to side i use to get is all but gone. maybe an inch side to side with no give. And as far as going backwards, with the acceleration of the shifter kart I noticed that it stops the helmet and ultimately my neck just at the point where i think it getting to far back. The only thing that I havent felt yet is the forward support. But then again in a shifter kart your head is always pinned back…. HA.
As for lab results and testing I have neither seen or read any. If you want to be 100% sure i would go with a HANS device. I also agree with what the nurse says above.