Selected Series style - opaque wider line

Is it possible to add an opaque wider line to the selected series line?

I’ve looked at setting the SelectedSeriesStyle and modifying the StrokeThickness and the Opacity.

If I set a larger StrokeThickness, then a wide line is shown.
If I set a small Opacity the line is opaque – but, as expected, the original line is gone (well it is now wide and opaque).

We would like the original style of the series to be unchanged but a wider, opaque line to be drawn in the same place.

Is the only way to add a new series with a wide, opaque line but the same values (and then somehow hide this series from the legend and the CursorModifier tooltip)?

Thanks
Andrew