Your manual mentions that Ev0 in the Histogram defaults to -3 stops below FS. This is about 12.5% of FS. Why this choice? Was it based on a standard metering constant i.e. K=12.5 and the setting point for ISO100, or was it based on a typical amount of clipping headroom?
Since 18% of FS is more common, perhaps an option to change the EV0 default to -2.5 stops below FS should be added.