Most people have a tendency to press it up against the roof of their mouth too hard for fear of it falling back and gaging on it. This is one of the main reasons why people get fustrated when learning to call. If you try and hold the middle/back portion of the mouth call with the middle/back of your tounge you are still abe to cluck and purr by "saying" the sounds you want.

benhuntin - you can also trim some mouth calls to fit the roof of your mouth. I like the Primon's calls my self.