another option is to freeze 16 or 20oz water bottles, and then santiize the outside and just float em in the wort.
then your wort volume doesn't change, and the risk of infection should be nil. I'd only make sure the wort was down to 170F so the plastic bottle doesn't melt/warp/get too soft.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10