3 will be a tight fit. I have a 7.4 cu Kenmore chest freezer. you'll be able to put 3 cornies and a 5lb CO2 cylinder on the floor, at least a half case of bottles on the hump, plus a tub of Damp Rid.
I put hops and yeast in the basket, over the hump.
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