Chris Miller UO/Falcons/Rams QB is a longtime friend and golfing buddy, I first met him because I autocrossed with his Dad in local SCCA events.
He went through a series of 6 concussions in short order. When he first moved to LA he was hit hard in one of his first games and couldn't find his way home, he had pull over and call his wife for assistance.
They were installing the battery for the QB's radios in the rear of the helmet which required cutting out the padding in the area. Combine that with the fact that the early synthetic fields were just a little softer than freeway concrete and it's no wonder why they were getting concussions.
I tried reaching out to some of the major off-road helmet manufacturers at the time to see if there was any interest in developing a helmet to address the issues........every one was a dead end street.