E3 focussing settings - advice please

I have just started to use the E3 to do school portraits and it is great, but I am not sure I have the focus settings set right for me. I shoot with two studio lights and a constant stream of subjects. Expressions (esp at under 5yrs) are fleeting and I turn on the setting to allow me to release the shutter when not fully focussed, so i know i get some mildly soft images at the expense of a great expression for the young ones, but I am not sure that i have my settings set up optimally.

A friend advised me to alter from the default to small area focus and select one focus point, which works fine most of the time, but even when i am not rushing and have the shutter priority release turned off i still get a few mildly soft images.... the eyes are not pin sharp.

What settings have you found work best for studio portraits?

Mike

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