I have used tumplines before. They are highly effective. But it is a piece of gear with which you need to start very slow, using a broad tumpline on the head, and very light pack weights to start with. And make sure you have a good angle on the tumpline. You can do a real number on your neck if you put too much stress on it too soon, before you have built up the muscles and muscle memory to keep the head and neck positioned correctly. Just one slip is enough to cause a great deal of pain, and not a little damage. And make sure you do not slip the tumpline down onto your forehead. It should be just forward of the top of your head so the weight is carried down on the spine, not backwards against it.
But it really is amazing how much advantage a tumpline can provide. I highly recommend them, as long as you do not have any cervical spine issues. If you do, or suspect you might, check with a doctor before using a tumpline. That is the only reason I do not use one now. Have not even thought about tumplines since my spinal troubles started.
Just my opinion.