For frequently accessed items, i.e. drinks, we use a
50 quart Igloo Ice Cube Cooler tied down on the aft galley seat with straps and hooks into 4 eyestraps mounted on the seat. As advertised, it holds 75 cans, with little to no room for ice, in 3 layers of a 5 x 5 array. You can remove the center 3 x 3 and fit four 1/2 gallon milk jugs, but they have to be frozen carefully, with no bulging or squeezing out of shape. Here are 25 cans and the four jugs. A total of 32 will fit around the milk jugs, which stick up about 1" above two layers of cans.
As you can see from the cooler wall thickness in the picture, this isn't a 5-day cooler. Even with the top layer filled with frozen milk jugs or frozen bottles of water or Gatorade, even 4 days is pushing it, as is 3 days with cube ice.
For infrequently accessed items, i.e. food and milk, we use a
36 Quart Coleman Extreme 5-day cooler in the factory cooler tub under the dinette seat. This will almost exactly fit 10 frozen 1/2 gallon milk jugs, but as above, they have to be frozen carefully with no bulging or squeezing out of shape. We've managed to go for 5 days and still have ice in the jugs by using 7 jugs of frozen potable water, 1 jug of unfrozen milk, leaving two jugs' space for food, much of that frozen (i.e. the meat and one out of two cartons of EggBeaters). We didn't do as well with cube ice.
I believe it was Greg who said the
60 Quart Igloo Ultra Cooler will fit on the aft galley seat. I note that although they use the "Ultra" name they used to use on their 5-day coolers (before they renamed them MaxCold and painted them blue), Igloo does not designate this cooler as a 5-day on their website for it, nor do they note it has insulation in the lid, just the body, like the 50 quart cube. I'd also want to make sure it left room for tiedowns.
The "cube" coolers also don't have latches, so I've bought some to keep ours closed in case we get knocked down on the starboard side.
71.5 is alot of difference, depending on what it is you are measuring. 