Best practice for positioning within Sencha Touch

Best practice for positioning within Sencha Touch

This is another attempt of asking this other SO question about positioning
and layout in Sencha Touch. In the previous question I phrased it more as
a philosophical question, here I'll present a specific, practical example
and question.
I would like to create a view in Sencha Touch that displays two lines of
text centered and positioned say 30% from the top of the view, and a big
graphic also centered and positioned say 50% from the top of the view.
Whats the best way of accomplishing this within Sencha Touch?
Also please note the graphic should be proportionally sized, it should
always be, let say 75% width of the view - since this should look
correctly across various devices.
See mockup