Upvote:0
You can try the following to continuously focus on the upper lip:
Having said this:
So if your concentration is weak to be at the upper lip where the feeling of the breath is the very subtle increase the area to include the tip of the nose or even the top of the nose.
Upvote:1
In the words of the Buddha, "pari-mukham satim" (step 0.5) in the sutta: http://lucid24.org/sn/sn54/sn54-003/toc-addon/index.html
Translated literally means somewhere near the mouth area. In the vinaya, pari-mukham can refer to chest hair area, facial hair, so if you take the physical interpretation of that phrase, it's not exact, and most people translate it in physical spatial terms as "in front".
There's also figurative a meaning, "pari-mukham" meaning to make that that main priority, the main task. Just like in the English expression, "focusing on the task at hand". It doesn't literally mean the spatial location of your hands.
So the answer to your question is, it doesn't really matter exactly where near the mouth you focus. 16 APS anapana isn't about that. The point is to use the breath as a way to fill up the entire bandwidth of your attention so you stop unprofitable thinking, and then thinking itself (mental talk). Using the mouth area as a spatial focal point is just a suggested preliminary way to achieve that. The important part of 16 APS is to develop a calm, lucid state of mind that uses the pleasurable experience of attending fully to the tactile experience of breath sensation pervading the body as a natural incentive. It's easy to enter samadhi when the mind is happy and occupied. And the mind is much happier when it doesn't feel constricted, stuffed into a tiny box.