I'd just like to share something in case its useful to anyone else: I was trying to make the header taller, so that it can accommodate images up to 200px high. 980x120 is just too wide and short. So I searched and I only found one reference in the CSS: in #header. So I overrode that in my child-theme's CSS, then I found another reference in the functions.php file: define( 'HEADER_IMAGE_HEIGHT', 120);.
I thought that changing this in my child theme's functions.php file would not override it, since it is loaded before P2's theme. But it did. I just pasted that same line in but replaced "120" with "200" and it works great! Just FYI, if its helpful to anyone.
