in the pwgallerydd/galleries/slideshow_dissolve/css/common.css file, edit the top and left settings of the .pg-sd-controller selector:
.pg-sd-controller {
background: url(../images/controller.png) no-repeat;
height: 42px;
left: 50%;
margin: -61px 0 0 -119px;
overflow: hidden;
position: absolute;
top: 50%;
width: 238px;
z-index: 10000;
opacity: 0;
visibility: hidden;
}
try using 85% as a starting point, you may need to adjust from there to get the desired location.