i had to replace my idler wheel because i dropped my bow and the wheel was damaged. martin parts are hard to get in austria, i found a shop in germany who had martin ilder wheels but only 2011 models and my bow is a 2012 bengal. the guys from the shop said that it would be compatible with a 2012 bengal. when i finally got the wheel and installed it, i noticed that there was still some space between the limbs and the wheel and the metal spacers from the old wheel werent enough to close that space. so i used the plastic spacers the shop sent me with the wheel.
I am a little confused of why a 2011 idler and 2012 bow, I believe that is what I read in your other Post. Still, properly shimmed the idler should be centered between the limb tangs.