9" is pretty long. Only 2 more inches but when strapped around your head, it's noticeable. I think 7" is ideal for the Proflex - i remember there were a couple masks that came with a 9", like the JT X-Fire. It may be ok, just the buckles on the strap will be slid further apart. But too far and they'll hit the ears, and then it won't get any tighter, unless you cut the ears or force the buckles through the strap slots, which could just rip the ears.
I wear hat size 7 3/4, and i need to tighten a 7" when wearing a proflex.
Last edited by nerdcore : 06-11-2013 at 04:06 PM.