This isn’t something the plugin does currently, so I’m going to move your post to the ‘feature requests’ section.
It seems to me it’d be more useful to have a ‘bigger map’ link that makes the map bigger in the page, rather than opening it in a popup. Would that work for you?
[mappress poilist="true"] <a onclick="bigMap(); return false;" href="#" rel="nofollow">Bigger Map</a>
‘mapp0’ is the name you assigned the map using the shortcode parameter [mappress mapname='mymap']. If you haven’t set a name the plugin will use ‘mapp0’ for the first map on the page, ‘mapp1’ for the second, and so on.
I hope that helps!