Off Table Neckwork?
I have done some of this as well - it can be great for many issues. However, instead of having their head off the table, I might have them supine with a pillow under their upper back, or supine on a Bodycushion with the head support removed, etc. Practitioner body mechanics are very important, as I know one MT who had overuse issues with her hands and forearms from holding the head up too much.