The CData define the pixel colors and are not scaled to the actual size of the UICONTROL.
If you need to rescale the image defined by CData, you have either to use an image, whose ButtonDownFcn simulates the Callback of a button, or to implement a ResizeFcn callback, which resizes the CData e.g. by imresize() and update the CData manually. Both methods are not trivial.
I'd prefer to adjust the positions of the UICONTROLs, but not their size.
