On a second thought, I think you can use the following javascript code as temporary workaround.

Put this code between album tags:

Code:
<script language=javascript><!--
calcsize(<!--[volume]--><!--[track]-->
<!--[tracksize/]-->+<!--[/track]--><!--[/volume]-->0);
//--></script>
In addition, put this code inside <head> tag of your HTML:

Code:
<script language=javascript><!--
function calcsize(size){ document.write((size/1048576).toPrecision(4)+' MB'); }
//--></script>
It worked for me