If you want to have the product designer to stretch to the full-size when using it in a lightbox as in this example, you can easily achieve that with some CSS tweaks.
.fpd-modal-product-designer.fpd-modal-overlay>.fpd-modal-wrapper {
padding: 60px 0 0 !important;
}
.fpd-modal-wrapper > .fpd-container {
height: 100% !important;
}
.fpd-modal-product-designer .fpd-done {
position: absolute;
top: 0;
left: 10px;
}
.fpd-modal-product-designer .fpd-modal-price{
top:0;
left:100px;
}