Back to the aiming of your knuckle, is this what McBeth is doing when he's lining things up? My putt is similar to his as well but I don't aim the disc directly in front of me, wish I could explain, maybe a video of me putting is in order. It appears he's aiming/focusing on his disc or hand or knuckle just before he draws back, might have to try something similar to that like the knuckle thing you suggested.
It took me forever to get my grip to feel right on my putter, I used to always line my index finger along the bead and it did generate good spin but I would miss left or right half the time. I had tried to curl the tip of my finger under the lip occasionally but then I would get that ugly wobble with NO power! Things started to come together a little more when I fixed my grip and made myself curl the finger under the lip until it felt right and (this was the big discovery>) got my weight transfer timing under control.
So the new grip, the timing of my weight shift allowing me to simultaneously pop the disc forward as my rear leg pushed off generated plenty of power and eliminated that ugly wobble. The putts started slamming in nicely even from 40+'!
All I need to fine tune now is this right of basket issue. I've read and heard several times before that some will aim LEFT of the pole, this always seemed to boggle my mind, I mean RHBH you Know your disc will hyzer out so why would I line up and aim even MORE left?! I aim dead center pole every time and nail it 60-70% of the time, the other 30% is the right side miss, I may have to force myself to aim a little more left of the pole and see how that works out, and the knuckle trick, kind of follow through like a golfer does with his stick on that same line.
Thanks for the suggestion, sorry for the long post.