I use p -m for that section, mainly because it was marked that way in the first arrangement I learned from.
But then as I got better, I tried different right hand methods and discovered that p -i made my hand more tense.
Try placing your left hand lightly over your right as you alternate p - i and then p -m and p - a. For me, my hand and especially the big thumb muscle is much more tense with p -i (leading to errors with the thumb stroke). p-m is the least tense and p - a is also good.
But then maybe my hand is weird?