I tweaked @lisa_zagari's awesome code so that the arrows are in the vertical center of the image, and overlapping the edges by a little bit. See code & example. Hope this is helpful!
.summary-carousel-pager .previous {
position: absolute !important;
left: 5% !important;
right: inherit !important;
top: 45% !important;
}
.summary-carousel-pager .next {
position: absolute !important;
left: inherit !important;
right: 5% !important;
top: 45% !important;
}