A system for configuring a hearing device comprises an in-ear listening device; a plurality of customization components for use with the in-ear listening device, each customization component when in combination with the listening device cooperating with the listening device to define a controlled amount of venting; and a self-fitting assistance processing device in communication with the in-ear listening device, which adjusts a gain of the in-ear listening device according to the amount of venting provided by a selected one of the customization components.