How do I optimize file size in excel 2007 workbooks with pivot tab
 

I am created large workbooks with as many as 16 pivot tables within. I have
three data sets that drive the tables. As you would expect these files are
quite large at around 40megs. Everytime I refresh the data the file size
increases. All tables from the same data source seem to be linked, thus
should be refferencing the same cached copy of the data. I have uncheck the
"save source data with the file" and "enable show details" options and have
saved the data in a seperate workbook. Asside from zipping them is there
anything more that I can do to reduce the size of these files?