The end of the fly line inside the braided loop does not butt up against the loop end, which is why there is a thin section near the loop. That will prevent full transfer of energy from the line to the leader, when casting. (hinging). If you leave that braided loop on, I'd advise cutting the shrink tubing off, then working the fly line all the way in, so it butts up against thick section of the braid. Secure it there with a drop of crazy glue. Then tie on about a half dozen wraps of mono with a nail knot, over the frayed end of the braid, where the shrink tubing used to be. Before tightening the nail knot, make sure the braid is pulled tight up the fly line. Then nip off any frayed ends of the braid above the nail knot, and apply a dab of crazy glue, Pliobond, or other coating to that knot. I prefer Pliobond, since it stays flexible, and lasts forever.