Stacking View for a Deck

My first module is nearly born, however, here’s still a problem I couldn’t figure out:
I want to show thumbnails when mouse move to a discard pile(which is a “Deck”).
I added a Mouse-over Stack Viewer in my Main Map Window, checked “Draw pieces”, selected “from all layers”, and checked “Include non-stacking pieces”.
Now I put some cards to discard pile, no thumbnail shows. Even if I check “Include top piece in Deck”, one thumbnail will show.
But what I want is to show all card thumbnails in the discard pile deck. What else should I set?