white space below header image

I have a large block of white space between my custom header image and the rest of the front page content. I reviewed the queries about problems with white space below header image posted previously (June 2014, April 2015) and the responses.
One was to copy the header.php in to a child theme and adjust the values. Changing the ‘flex-width => true, to ‘flex-width’ => falseand ‘flex-height’ => true to ‘flex-height’ => false was also suggested. This did not work for me.
Another response explained that the “header CSS is controlled via a custom function targeting the parallax-bg ID and can be found in functions.php starting @line 345. As the code is hooked to the wp_head action means it fires after all other CSS have been loaded and therefore the custom CSS you are adding has no effect since it is loaded before the function.
In order to override it you’ll need to use a child theme, add the function to your functions.php, edit as required and then set it fire on a higher priority of say 10 or 11. So in your code the add action line would be something like add_action(‘wp_head’, ‘itek_internal_css’, 11); “
I tried this approach also, and did not achieve the desired goal of reducing white space, though I may not have coded it correctly.
Finally, a friend suggested that the excess white space might be the result of a top-margin attribute that was too big. I have tested reducing the top-margin attributes that seemed most likely with no apparent reduction of white space.
I would appreciate any insight you can provide. Thanks!