Q3DBars: Be able to control the spacing between bars in different series but still keep a margin around them on the plot

Q3DBars: Be able to control the spacing between bars in different series but still keep a margin around them on the plot. Currently if you use the barSpacing this influences spacing for all bars in all series, so setting it to QSize(0,0) would effectively fill the section, whereas it would be nice to have a gap but still keep the bars in different series together.