Here's how I installed mine:
I used industrial strength velcro to hold the fans to the helmet. I can easily take the fans out or push them down if I need to take the helmet on or off. The velcro holds the fans in place just fine. The only problem is I attached the velcro to the rubber padding, and it doesn't hold up very well in heat. Today, it got up to 108 degrees, and I found the velcro holding the batteries had become detached from the padding.
Other than that, this configuration really does the job. Easy to breathe, no overheating, and the fans don't even touch your face.:cheers I really noticed the difference when I forgot to turn them on ... within 5 minutes, my visor was completely fogged over, and my head was a swamp.