peakrut,

You wold not only need a new string but also a new set of cables since the new idler wheel setup utilizes two short strings and a cable, or a short string and two cables (depending on the way you look at it).

I think your biggest concern would be how the new idler wheel will impact the rest of your bow..ie, the limbs, draw length, draw weight, etc....

Call Hoyt directly and ask one of the folks at their service department.