How far forward do I go with my mouth on the mouthpiece?

[wshNPC]

all the way to the bumper?

[windsynthhelp]

The metal piece you see at the end of the mouthpiece (I think you are referring to as the bumper) is actually an additional sensor. It is called the lip sensor (or extra controller) ... while playing you have the ability to touch this sensor with your lip. The value amount of MIDI data of a particular controller reacts in proportion to the amount of surface area that your lip touches. So if you press super lightly against it, it produces a smaller value. As you press more lip against it, it increases in value.