In case anyone else reads thru this, here’s what I found:
1. Adjust width and height in functions.php at lines 33-35, genesis-custom-header
2. Adjust min-height in style.css at line 690 for class .header-image and id #title-area
Bam! Your logo will now fit. Be sure that your logo’s background (even if it’s transparent) is set to 1152 pixels wide*, or the cropping tool inside of Genesis / WordPress will kick on and try to fill up the width with a cropped version of your logo.
*I have not yet tackled the responsive aspect of the header image, so this will break responsive design, I believe.
-DonO