Backstay adjuster
I have a different brand of furler on my 24 ft S2, which fits over the turnbuckle and hides it from view, so I am not an expert on Furlex systems. However, if the turnbuckles are tight and you still have slack in the system, you may need to shorten your forestay, or better yet, install a backstay adjuster. If your backstay is split, you only need to rig up a system with two pulleys with metal sheeves, a large ring (or better yet a triangle) and a 4 to 1 ratio block and tackle (like a boom vang). Put one pulley on each of the split backstays. Connect the two pulleys and the block and tackle with the ring and attach the other end of the block and tackle to a strong point on the transom of the boat. When you are out sailing, pull the block and tackle tight, which will cause the two pulleys to ride down on the split backstay, forcing the mast backwards and tightening the forestay. The racers do this all the time, it causes the jib to fly better, since there is no sag in it, the roller furling will probably stop rubbing and you can release the extra tension when the boat is at the dock by simply releasing the block and tackle.
