Disable Aspect Ratio Crop on Custom Header Image

Hey Guys,
I have this set in my functions.php file:

define( 'HEADER_IMAGE_WIDTH', apply_filters( 'basic_header_image_width', 500 ) );
define( 'HEADER_IMAGE_HEIGHT', apply_filters( 'basic_header_image_height', 150 ) );

And when a user uploads a new image, they are forced to crop the image to maintain the 150×500 aspect ratio. What I think it should do is allow the user to crop the image, as long as it fits within a 500x150px box.

Is this possible? If not, I’d rather turn off the cropping feature all together.

Thanks,
Drew