<div id="map_container" class="routeMapContainer google-maps" title="" style="height: 896px; position: relative; overflow: hidden; transform: translateZ(0px); background-color: rgb(229, 227, 223);">
just edit "height: ###px..." to the value you want.
Perhaps someone knows enough about javascript to write a plugin that would access the DOM "map_container" box and increase its height.
Hope this is of use.
Cheers
Drew