Calf tail can be rather bulky and slick. Try working with less material and see if that helps. Too much material at the tie in point and the whole thing will rotate and move around on you.

If you want a real dense wing you might try attaching it in 2 or three layers.

To get a good taper I grasp the butt ends and bend them up 90 degrees from the hook shank, then holding my scissors parallel to the hook shank I slice through the bundle, cutting from front to back. With practice this should give you about a 45 degree taper. I then wrap the cut ends towards the hook bend with loose wraps, increasing thread tension as I wrap down the slope. Then wrap tight wraps back up the hill with heavy tension. The first layer compacts the fibers, the second layer locks them into place. Pull the wings up vertical and wrap a thread dam in front to post the fibers upright.