I purchased the pin-less plastic peepers - there are little plastic stubs that go into each nostril. I must admit, I was also concerned at first, but given the alternatives felt I had to try. Within minutes of putting them on, the hen went back to "normal" - pecking around, scratching, no problems at all. Does not seem to impact breathing, eating, drinking or normal behavior.
I used the plastic peepers as they don't require a special plyers. Very easy to put on. I warmed some water in the micro and put the peepers in to get them softer. With my DH, we got them on each bird in a matter of seconds. The reaction of the flock to the first few peeper-wearers is pretty hysterical - everyone stands and stares. Then, life goes back to normal!
I really am curious to see how/if behavior has changed when I take them off in a few months.
Corporate Granola - please do let us know how it goes. It certainly has made peace in my flock, and saved me from having to rehome any of my sweet hens.