Divergent Stacked Bar Chart - problem with 5 point scale

Firstly,

Apologies if this is repetitive but i've looked at other threads and still can't resolve the issue. My stacked bar graph looks very busy so i've attempted to convert it to a divergent stacked bar chart, however I can't get the neither agree/disagree to sit evenly over the 0.

When I try to split it I end up with one half at zero and the other half after disagree. And I can't seem to get the formula to work either.

I've attached a sample to the stage I seem to be able to get to before the problems start.

Appreciate and advice on this matter. From a frustrated student.

Thanks