First, activate AF on the AF-ON button for AF only and use AFC (continuous AF camera setting). Then focus on your subject or to the closest focus distance for your lens (depending which magnification you desire), then release the AF-ON button to lock focus. Now holding the housing with your right hand only (housing must be relative neutral for that off course) while holding your body position with support from your left hand (holding on a stone but not a coral etc; I also like to use one of these Lembeh sticks). Now you move slightly the rig back and / or forward until the object is fully in focus i.e. appears sharp in your viewer (a magnifying viewer especially one of those 45 degrees viewer will help in this respect); immediately press the shutter trigger and take the image.
With manual focusing you will need both hands on the camera and will miss in critical situation or make it impossible to take a sharp image in currents.
bulkhead and internal HDMI cables (within camera housing): 100 (approximate, not measured)
total additional: 528
grand total approx. 2.2 kg
If Nauticam speaks of around 1.0 Kg then it is only the ninja housing, I guess.
To counterbalance the additional weight (and some of the negative buoyancy I had before already on my setup) i have added 2 of the new Nauticams' carbon arm floats. Each of them give me around 250 g of a lift underwater.