I have a progressive 416 that measures 13.5" eyelet to eyelet on center. It came with a K75 low seat that seems to ride lower than my other K75 low seat. But there are other variables there, I.e. stock vs custom seat. I seem to remember my last Progressive 420 at 13.75 and the new YSS I just got also at 13.75. Not an expert but wouldn't whether its a low shock depend more on the measurement at the center of the adjustment range, not the lowest setting?
Also, what kind of shock is it? Are you measuring the eyelets on center? Finding the model # might help determine what the specs are.
For what it's worth...
Van