I am using Shackle + Spinner's on my magplar heavy armor build. I prefer spinners to innate axiom on a magplar because it gives more max magicka which synergizes well with breton and shackle, but most importantly it is more effective with ultimates. As well all know, magplar ultimates suck. I use meteor and Spinner's makes it hit a lot harder while innate axiom is kind of useless in that regard. And heavy armor can use all the extra pen it can get.