Graph Secondary Axis align to zero of primary axis

BryNeedsToExcel Replicated the relationships in your graph to demonstrate a work around.

The automatic secondary axis boundaries go from +100% to -200% with gaps (major units) of 50%. Thus, two gaps above 0 and four gaps below zero. You need to reformat the primary axis and use the same relative boundaries. So, the maximum value = 700. Divide in two = 350. Multiply that by -4 = -1400. Now, override the primary axis bounds and set them to -1400 (minimum) and 700 (maximum) and set major units to 350. Play round with the placement of the axis labels and the format of the axis itself, and you may come up with something like this.

I am totally aware that this is not very practical in case your graphs keep changing all the time, as you would have to recalculate the axis bounds every time. But, it's a workaround for the instances you really need to align the zeros on both axis.

Attached a file for your convenience, so that you check out the settings.