Is that the side of kielder with the 1.2km raised wooden bit (thats plenty wide enough to ride side-by-side (and had quad bike tyre tracks along it when I went). A fair few sections were really quite rough, and there was a far too long fireroad descent early on?
I’d echo your comments
The east hillside (up/over, deadwater? trails) I like very much though. The end (after the turnoff for the black) didn’t leave me amazed, but I really liked the black section. I found the trek up onto deadwater dell interesting, but probably only because it was covered in snow when I went, so the descent down again had some speedy suprise lumps and bumps in it
I know its not popular but I quite liked the XC trail at newcastleton (20mins (by car) around the other side of the west hill). The black north shore stuff there was very wet and I wasn’t feeling upto falling off that day, though I’d very much like to go back now I’m a bit better with raised wooden stuff