Well it seems that Jackster understood what you were talking about.
If you want to use a braided loop here is how I would do it.
1. Take a round tooth pick and stick it in the end of your fly line and remove the tooth pick. Then place a drop of a water proof super glue, but use the thin stuff on the end of the fly line. You want it to suck into the braid of the fly line. This will seal the end of the fly line so water won't migrate up the braided core.
2. Now feed your braided loop onto the fly line all the way up to the loop knot.
3. Toss the heat shrink and get a piece of 10 or 12 pound mono about 18" long. Tie a nail knot right at the end of the braid farthest from the loop. Before you pull the nail knot tight make sure the fly line is all the way into the braid and then tighten the nail knot.
4. Trim the knot ends and apply Pliobond, or some glue that stays flexible, over the nail knot making it as streamline as you can. You may have to apply more than one coat of Pliobond to get the nail knot covered like you want it. You don't want a big glob of glue, just enough to tidy things up.
So now you have the braided loop nail knotted to your fly line and the nail knot is covered with Pliobond and you are ready to fish.