Up here in NY state, I have suggested this for years. A big bag of ice, still in the plastic, shoved up into that chest cavity and belly area WILL keep a carcass pretty darned cool. The hide and layer of fat will become a pretty good insulator. Thats IF the carcass gets cooled off right away, first.

What it wont do is keep the head. neck and skin cool enough for us taxidermists. I agree with you guys who suggest taking care of the first one before worrying too much about shooting more, but that bag of ice is good insurance in between.