just going to be doing some elk summer sausage this weekend(which is why I needed to know about temp gage) but the recipe I have(Jalapeno/cheddar SS) is calling for fatback. What is fatback?? and can I just use a pork butt.....I was thinking on doing 80% elk/20% pork butt. Will this be enough pork fat, or would a mixture of 70/30 be better(not as dry)