Found it.
visit:
/includes/booklet/booklet.php
Tweak this to change sizes.
Messing with the ‘var bookletSide’ is what I specifically needed:
/*—– Set variables —–*/
var booklet = jQuery(“.wp-booklet-<?php echo $instance_id ?>”);
var bookletContainer = jQuery(“.wp-booklet-<?php echo $instance_id ?>-container”);
var bookletThumbsContainer = jQuery(“.wp-booklet-<?php echo $instance_id ?>-thumbs”);
var bookletExpanded = jQuery(“.wp-booklet-<?php echo $instance_id ?>-expanded”);
var pageWidth = <?php echo $properties[‘wp-booklet-width’] ?>;
var pageHeight = <?php echo $properties[‘wp-booklet-height’] ?>;
var pagePadding = <?php echo $properties[‘wp-booklet-padding’] > -1 ? $properties[‘wp-booklet-padding’] : 10 ?>;
var bookletWidth = <?php echo $properties[‘wp-booklet-width’] ? ( $properties[‘wp-booklet-width’] * 2 ) : 560?> + (4 * pagePadding);
var bookletHeight = <?php echo $properties[‘wp-booklet-height’] ? $properties[‘wp-booklet-height’] : 380 ?> + (2 * pagePadding);
var bookletSide = 74;
var thumbsSide = 11;
var bookletContainerWidth = bookletWidth + bookletSide * 2;
var bookletThumbsContainerWidth = bookletWidth – 22 ;