Colorbox doesn't open at proper height when first opened

So I'm using the colorbox plugin for a contact form. I am just the default colorbox properties, so it should automatically adjust to the div it contains (right?).

Well There is a small vertical scroll bar on this colorbox content when its FIRST loaded. I've seen it happen sporadically in Firefox and chrome for OSX

attempt #1

$("a.modalAutosize").each(function(){
    $(this).colorbox();

});

active code on example

$("a.modalAutosize").each(function(){
    $(this).colorbox({onOpen: function(){$.fn.colorbox.resize()}});

});