I do think though that beyond a certain point, this whole root orientation thing becomes an obsession. The mere fact that that root is curved, for example, may not matter in the slightest to the tree's long-term performance. Again, I'd cut any obvious girdlers and forget about it. Maybe because I've read too many studies showing that, for one thing, wherever a girdling root is cut, two new roots may form in such a position that one or both of them could end up circling around an expanding trunk base themselves some day! 'Tis true....this can happen. And again, not every species is equally impacted by such roots.

+oM

Centre,
I would cut that root myself. Not all the way back, but at the point of the second kink where it really turns a counter-clockwise direction. If you want to wait till leaf drop, then that is fine. I did the same to out Autumn Fantasy Maple (also a hybrid red x silver maple), and it never seemed to notice. I also did something similar to out Shantung Maple while in leaf, and it never seemed to care. I would also go a bit deeper to see if there are more roots just below the current ground level. But really your probable about as far as you need to go IMHO. Lastly, relax. Your doing just fine, and we are all here helping you because we want to help you.

Arktrees

Thanks to everyone for your help.