With the newest software you can hide all the readout boxes in any sonar view..
And you can hide all but COG in the box #2 of any chart view ...
In most software versions (except really old versions) all the Readout boxes can be hid and depth and temp is overlayed in the lower left in the "Full Screen SI" view only... This setting is called "Readouts Off" under the Sonar tab in the Main Menu System ...
Rickie