Milestone aspect ratio in pgfgantt adjusted for units?

So: I have a Gantt chart created with pgfgantt where in order to fit my pages I have included

x unit=1.4cm,y unit chart=6mm


in its preamble. This means that milestone shapes are spread out horizontally. How can I change the vertical and horizontal units of a Gantt chart in a way which doesn't affect the aspect ratios of elements like milestones?

• You can always declare a new milestone element with an aspect ratio inverse to new x unit and y unit ratio. You must declare a new milestone because pgfgantt milestones doesn't consider aspect ratio as diamond original tikz shapes does. – Ignasi Oct 27 '14 at 10:15
• Please consider to provide a minimum working example showing your problem? This way will be easier to help you. – Ignasi Oct 27 '14 at 10:17
• Thank you - I can't however, find a way to set the aspect ratio of an element, nor of setting the width and height. – Alasdair Oct 27 '14 at 10:34
• This is the reason because you must use a newganttchartelement as is explained in pgfgantt documentations – Ignasi Oct 27 '14 at 10:36
• According to my documentation (v4.0), the relevant keys are left shift, right shift, top shift, height. But there is no width, or aspect ratio. – Alasdair Oct 27 '14 at 10:52

If I understand your question correctly, then you can use xscale to adjust the aspect ratio. For example:
\begin{ganttchart}[