i have done a few visualizations like this and have found that utilizing a computation for the measure value so that they are multiplied by -1 to make positive into a negative (or vice versa) and then using this measure rather than the original, you can line up the values as desired. Note that the value will still be negative though. Do you have a sample viz? We could probably format the values using abs() to always appear postive if the view allows.
That is what I am doing. But I added a workaround. I am still using the actual values but sorting based on the multiplied by -1 values.