Tippet or Leader??
I started to reply to your post earlier and then, I thought I would see what other comments were given that are related to your question. For many, many years I have pursued the art of tandem rig nymphing by using just plain tippet material. The biggest reason that I stayed away from using tapered leaders was because of the memory coils that are so hard to get out of a tapered leader. At this time of the year when the air and water temperatures are pretty cold in the early part of the day, you will see both flyline and tapered leaders really holding onto kinks and coils from being on the reel. A good soft 8ft. piece of 5X tippet works much better if the flies that you are using are weighted. This piece of tippet material is tied onto a loop connector with a Pitzen Knot and then onto the fly with a Pitzen Knot. If you choose to use a dropper, then it is tied onto the hookbend of the top fly with a Pitzen Knot tied in the air, and finally the dropper fly is tied on with another Pitzen Knot. The purpose of using this particular setup is to have a fly coming back downstream toward you that is about as straight and unencumbered by slack or coils as it can be. This is one of the best ways to fish nymphs consistently and be able to detect strikes that I have found. One of the quickest ways to see the difference in the two methods is to stand at the top of a hole where water is pouring over a set of rocks and place a short lob into the head of the hole. With the line about 6 inches out of the water, look at the line that is between the water and your flyline. You will see coils if it is a tapered leader. That means slack! It is hard to detect strikes with slack. Do the same thing with a section of tippet material. You will see a slight arc from the flyline to the place where the line enters the water if you do not put any tension on the line. That puts you in direct contact with what is going on down deep where your fly is moving with the current. You can detect strikes much easier and respond to them if you need to set the hook. The biggest difference in fishing this method is that you will make a softer and more rounded type of casting stroke than if you are fishing with a tapered leader. Give this method a try and see if it does not work for you.