The obvious workaround would be to not use that kind of 3D chart, but stick to 2D. Any BI professional with any knowledge about data visualisation will strongly discourage the use of 3D charts because they distort the data, are often inaccurate and are hard to read. There are some kind of data sets that cannot be visualised very well in 2D. Your data does not fall in that category. A 2D bar chart is by far superior in your case.
I'm terribly sorry about the purity of the data representation, but this is a specific user (== one writing the cheque) request to use that type of graphic. Oddly, users frequently want things that do not fit into an IT-perfect scheme of things. Your answer reminds me strongly of the great Tommy Cooper joke. Man goes to Doctor:
Good thought: a 'static max' isn't static as you can put an expression in there. These graphs are being generated out of a DB, so I don't know the max until the selection is made. But given I can use an expression, I presume I'll need to generate a max dependant on the current data.
I'll play with this - though it might take a bit of time!