Hey.
Training front, middle and back2 has a consequence on front and back3, but these ones are hung, in my experience, more openhanded.
As for back2 pockets, from the deeper ones I moved to the others on the same line, then to the smaller pockets in the bottom line.
Never tried to use the rungs for back2.
And yes, depending on fingers' length, you have to position you r hans in specific ways to generate the adequate force and grip.
Hope this helps.