@emclab try to set containerStyle={{height:30}}
AND leftContainerStyle={{height: 30}} OR rightContainerStyle={{height: 30}}

Can anyone else answer this question? The above answer is incomplete. And yes, the default header is too big in terms of height, so I tried to apply a height="8%" style using ContainerStyle property, which did reduce the size, but all the header components (within the header) are still vertically aligned at the bottom, and there is some unused space above the title etc that seems unnecessary - if we could align the text to top, I can easily reduce the height further using a lower value than 8%.