@mixin homeSlider(
    $dim: 150px,
    $h1: "h1 { font-size: 4em; margin-top: 0; }"
){
    section {
        margin-top: -$dim;
    }
    $h1;
 }

 @include homeSlider( $dim: 50px, $h1: "h1 { font-size: 3em; margin-top: 0; }" )