do you have a screenshot of the problem?
what type of layout container do the charts reside in?
There are 2 VBoxs stacked vertically. I added the red borders just to visualize the problem. The upper VBox contains a bar chart. The first circled area shows the place where the upper VBox meets the lower. The lower VBox contains 2 (empty) line charts with red borders around each linechart. You can see in the lower circled area there is a larger space. I believe that is the area that would be occupied by the horizontal axis. It's actually there but with an alpha of zero. Notice also that the unit lines line up between all the charts which is what I want. However if I try to remove the horizontal axis with .visible and showLabels, it causes misalignment of the charts as in screenshot 2. I believe that is because the overall horizontal width will include the horizontal axis even if it's invisible due to the alpha but it will not include it if .visible and/or showLabels is false and the last axis data value sticks out beyond the gray area. The red borders did nothing to complicate the problem.
I cannot think of a solution that would keep the charts lined up but have some with horizontal axis and some without and reclaiming that axis space.
Anyone from Adobe care to comment?