Sorry I’ve been missing - trying to do some catch-up here now.
Just wanted to add that from a brain-health perspective, I prefer to have people start with less and only do more of anything if that seems needed.
When I was using ICES coils on people’s heads, I tended to use 4-5 on most people and that gave them a nice response without much in the way of headache or other less-desirable effects. Some people were very sensitive after concussion and needed even less. I didn’t find anyone who needed more. I generally positioned the 2x2 coils, doubled, on each side of the head, hoping the doubling gave more penetration.
On myself, I’ve used the single coils and the 2x2 on my forehead for migraines, set at 3 and found it useful for the headaches and for my aging brain.