Found that oddly when you inspect the code for the swift slider is :
<div class=”swiper-slide image-slide” data-slide-id=”2″ data-slide-title=”Caged Boom” style=”background-image: url("http://caged.eu/Core/wp-content/uploads/2014/09/Caged-660.jpg"); background-color: rgb(0, 0, 0); width: 900px; height: 335px;” data-bg-align=”center” data-slide-img=”http://caged.eu/Core/wp-content/uploads/2014/09/Caged-660.jpg” data-style=”dark”></div>
As you can see its setting it at 900 x 335 even though maximum height set to 660 or 600