I put the gain ht whip antenna on the antenna analyzer and swept it with and without the tail. Massive difference. Sometime I will post the results here.
Now some will say that you are the ground via capacitive coupling when you hold the ht while keying up, and that a tail is not necessary or does very little. I’m still waiting for real world hard data to prove either way. Not just some person with an ego as large as they wish their cranium was.
Just to test both theories, as incomplete as my rudimentary tests were, I swept the 3 whips and all the stock rubber duck antennas that I had. In all cases, if I was holding onto the analyzer or not, the tail won out.
That is the extent of my analytical testing. Now for practical results. I have worked the same events both with and without. I have even started without and added the tail later. From my experience, it seems to make a difference.
Here is my personal take on it. If there is no harm in using one - my transmission will never get worse than without and there is the possibility that my transmission will be the same or possibly improved, it is worth using one every time... kinda like a condom.