One thing about mouth calls. Not all calls are made the same, neither are all mouths. You may have to try different ones to get a good fit. If you have a high palate (the shape of the roof of your mouth is tall and narrow) a slim design or youth model will be a better fit. Some calls have frames that can be bent to make a better fit others will break if bent. Different shapes on how the tape is cut can effect the seal. The most important thing is that a good seal is formed so that all air must pass over the reeds. Placement in the mouth is less important than seal. I know one fellow that places the call to side of his mouth almost against his teeth and he is better than I at running a diaphragm. I find top dead center the most comfortable.