AndyMan: It may help you to take a look at my post from August “Summer Sausage Nightmare” and the replies from Jonathan and others. Looking back, my problem was a lack of mixing the meat properly. I was not getting enough protein extraction, so the fat in the meat was cooking out during smoking. This left the Summer Sausage tasting dry and with the mouth feel of a sawdust log. I purchased one of the meat mixers from Walton’s and it fixed this problem. My small 20 pound mixer was not expensive and does a great job mixing the meat. It’s well made and easy to clean.
Also, by following the smoking times suggested by Waltons and keeping a pan of water in the smoker my sausage was “stalling out” in the last critical hour of the smoke process–never reaching an internal temp of 160F. Of course, your product must be brought up to 160F internal temp if you expect to be safe from food bacteria. We don’t want to make people sick with our sausage. For me, the solution, as suggested by several of the “Old Pros” who follow this site, was to stop smoking after about four hours and transfer the product to a heated water bath to bring the internal temp up to 160F. I was getting to 145F - 150F in the smoker, but couldn’t close the gap to 160F. About 15 min. in a hot water bath (slightly below boiling) did the trick. The sausage comes out of the water fully cooked, casings full and tight, without wrinkles, and the fat is fully emulsified.
Best of luck with your sausage.