When you say "stretch" please explain that process. (Sorry if this is something simple - I'm relative new to the conversion from analog to digital)

Hover the mouse pointer over the right end of the cassette clip on the timeline. It will change into a double-headed arrow. Hold the Ctrl key down and drag the edge until it matches the other clips. This stretches it out and makes it play slower. You can have the pitch drop as if the tape was playing slower, or you can have it retain the same pitch. To switch behaviors right-mouse-button click on the clip, click Properties. If "lock to stretch" is checked then the pitch will drop.