Use these settings [photospace horizontal_thumb=true sync_transitions=0]

Add this to style.css in your theme folder. You may need to adjust to suit the size of your gallery (see comments).

[css]

.photospace {
position:relative;
margin-bottom: 20px !important;
min-height: 200px; /* space for loader */
}

.photospace,
.photospace .thumnail_col,
.photospace .gal_content,
.photospace .slideshow-container,
.photospace .slideshow span,
.photospace .slideshow a.advance-link,
.photospace .slideshow img{
width: 100% !important;
height: auto !important;
}

.photospace .slideshow span{
display: block !important;
}

.photospace .gal_content{
float: none !important;
}

.photospace .slideshow span{
position: relative !important; /* Keep the gallery height – Doesn’t work with synced transistions */
}

.photospace .loader{
width: 100px !important;
height: 100px !important;
top: 50% !important;
left: 50% !important;
margin-left: -50px;
}

.photospace .thumbs_wrap2{
min-height:45px; /* space for thumbnails */
overflow: hidden;
}

.photospace .thumbs{
min-height:40px;
}

.photospace .thumbs_wrap{
float: left;
left: 50%;
position: relative;
}

.photospace .pageLink.next{
margin-right:0;
}

.photospace .thumnail_col {
float: left;
left: -50%;
width:auto !important;
position: relative;
}

.photospace ul.thumbs {
float:left;
}

.photospace span.image-caption{
position: inherit !important;
}

[/css]