When I've created my own cell renderers, I've usually cribbed the code for focus/selection highlighting from DefaultListRenderer. One thing that troubles me about that every time, is that noFocusBorder isn't loaded from the UIManager, it's defined in the implementation. And yet, it has to match the width of:
   UIManager.getBorder("List.focusSelectedCellHighlightBorder")
   UIManager.getBorder("List.focusCellHighlightBorder")

Right now it's just new EmptyBorder(1, 1, 1, 1);

If it doesn't match, I think the cells will wiggle. Shoudn't the noFocusBorder be
looked up too?