First off -- adding a loop WILL change your draw length!! It may not change the BOW'S draw length, but it will change YOURS. Adding a loop will increase the distance between your bow hand and your anchor point; assuming you keep your bow hand the same (including the relationship of the grip to the bow and eveything else), it WILL move your anchor point rearward. It HAS to; if it didn't, we could assume the loop was ZERO inches long -- which in turn means you didn't tie a loop on! Add a loop of ANY length, and it moves your anchor point rearward. To compensate and keep the EXACT same anchor, you'll have to decrease your dl, if only slightly, depending on the length of the loop.