I did one towards the back facing the back of my head and one on the other side towards the front facing towards the lenses. I assumed it would blow air around my head and towards the top. System is Henry’s got it from eBay. I was worried about facing both of them towards the eyes cause I have naturally dry eyes. Also if you plan on putting other electronics in there make sure you have that planned out as well. I’ve got an AM helmet and it’s still tight to get on. With two fans, the hearing assist, and the mic I can barely get my head in so I had to put them where I can. Anything is better then nothing in my opinion. Sent from my iPhone using Tapatalk