Whiting has capes just for streamers. I use them and they are great.
My I also suggest a few hints in tying streamers and getting the wing to stay on top of the body.
First I use 4 hackles for each wing, two to a side. You need that many to get a good full wing. After you get the body done foarm a small area with the thread were the wing will be mounted. Now take a pair of smooth jawed pliers and flatten the area were the wing will be tied in. This will keep the outer feather of the wing from rolling of to the sides. (Yes you can mount a wing without doing this but it is much easier if you take this step) Next take your 4 feathers and get them ready for mounting on the hook by matching two feather to a side and the the inside curve of the feathers to each other thus foraming a 4 feathered wing.
Now when you go to mount the wing on top of the hook in the prepaired area. Hold the 4 featers as they will be mounted on the hook, crimp the 4 hackle stem's with your thumb nail so they are "UP" in the air a bit were you will be tying them in. Do this right in front of the wing on the bare stem's. I use my thumb nail to do this. Again this will help the wing tie in easier and prevent the wing from wanting to roll to the side or separate. I hope you underatnd this.
Again it is much easier to show a person than explain things. If you do not understand just let me know and I will try and help. Ron