So the ultimate, never miss any finger unlock action strategy for me has been the following:
1. Install 703
2. Register a finger twice.
3. The first time through, use the meat (pad) of the finger and move it around, keeping it flat, and then for the second phase of the first finger read, continue to use the meat of the finger for the first read in the exact way you would press the button to unlock, and then alternate with a little right and left roll of the finger, and then flat again until you see success.
4. For the second register of the same finger, do it exactly the same way as the first finger register action, but instead of using the meat of the finger, use the tip of the finger, including a little of the meat (so not a dramatic tip up).
I know it has been suggested not to use the tip of the finger, but it appears that with a two finger registration combination as described, this has merit. I have not had one miss in three days. Maybe 40 attempts. It's working for me for what is worth. Feels more solid than anything else I have done as far as perfection.