I'm a fixed head fan and don't like mechanicals myself. BUT.... through testing some mechanicals and after discussing the same thing with Len a couple times, I found that foam and mechanicals don't react well together. If you place a piece of cardboard on the target they will open. The cardboard is more like the hide of an animal, foam isn't. Chances are they open just fine on an animal. It doesn't have to be heavy cardboard either. Just a thin box opened up and placed on the face of the target will allow them to open.