After about 10,000 rounds of 9mm loaded, I installed the Level 10 spring and bushing. No really noticeable sag at that point, although the Dillon spring was "bent" in the middle and wouldn't roll flat on a smooth surface. The Level 10 website doesn't yet list compatibility with the 1100, but it's worked great in my initial testing. Fits perfectly and operates smoothly. The spring gauge is thicker and (of course) much longer. No tooling marks on the bushing, looks great.
Operating the press feels smoother with a slightly easier return stroke. When you want/need to replace the original, I recommend this part.
Ed