Hello, 

First id like to say that its a beautiful and impressive theme you've done here!!!!

I struggle to find a way to hide the bottom border with transparent header.

I've tried to apply this custom css you advice to apply : 

But it won't work :(

If you have any solution, let me know

Best :)

body #header-outer[data-transparent-header="true"].transparent {    border: none !important;
}

Yup!

Thanks for reaching out anyway!

;)