I'm just going to throw this out there about the broken hairs at the top. It seems to be a buckskin/dun thing. When I used to show breed shows, even the horses that had a serious tail management program
had broken hairs at the top.
I know that what I was extremly paranoid about Odie's tail, I did every hair treatment, wax, conditioning trtments known to man & horse. It did look nicer than when I don't do all that, but I still had the broken hairs.
Otherwise to get more length, I just start a braid about 3" down from the bone, and roll up the braid, and wrap it in vet wrap (looks like a cocoon). But I would wait until after the flies go away. Even a short tail can get some flies.