Never mind, found a workaround.
Put the trend object in a container by itself, the same size as the container
Have the trend object layout anchored to all four sides of the container
Have the container layout set to relative, don’t maintain aspect ratio
Transform the size of the container, not the trend
Scaling of the realtime controls is correct, and I can adjust the size of the chart area to put my buttons underneath.
Workarounds in both cases, but at least there is one!