Decision between opinions on the shaving area

The early authorities disagreed on where the end of the sideburns area is (which has implications for shaving with scissors like a razor): According to the Rivan (Rashi Makkot 20, s.v. Shtayim), it is the end of the ear, as he wrote that from the place below the ear, where the lower jaw emerges and separates, from there begins the sideburns of the beard. Thus, until there is the sideburns of the head. According to other early authorities (Rabbeinu Chananel, the Rosh, the Raavad, the Meiri, and the Tur), it is until the end of the temples, and what is below this on the upper jaw is not part of the sideburns of the head, but part of the sideburns of the beard (and another opinion is the Ritva, who holds that until the end of the ear is neither the sideburns of the head nor the sideburns of the beard). In the Shulchan Aruch (Yoreh De'ah, Siman 181, סעיף 9), it is written that the measure of the sideburns of the head is until below the ear. And see in the commentators (Shut Eretz Tzvi, Siman 3, אות ה) who questioned why the Shulchan Aruch ruled according to a singular opinion against all the early authorities. Several explanations were given: A. In Shut Imrei Yosher, Part 2 (Siman 183, אות ב), it is written that the opinion of the Shulchan Aruch is that the sideburns of the head are until the middle of the ear, but he was stringent until the end of the ear because we are not proficient. B. In the notes in Shut Eretz Tzvi (there), it is written that the Shulchan Aruch holds that the place of the sideburns of the head is until the middle of the ear, according to the opinion of most early authorities, but because of the ways of the Amorites, it should be left until below the ear (see there where proof is brought from Midrash Devarim Rabbah 2, 18). C. What is written in the Shulchan Aruch "until below the ear," according to medicine, only the ear hole is called an ear (Sefer Pe'at Zekanecha, p. 48, in the name of the Gaon Rabbi Nissim Karelitz, shlita). D. In Shut Tefillah LeMoshe (Yoreh De'ah, Siman 20, אות ג), it is explained that what the Rivan wrote (which is the source of the words of the Shulchan Aruch) "below the ear" does not mean below the entire ear, which is under the ear. Rather, it means below the beginning of the ear (and not above the ear), which is on the side of the ear where the end of the head connects with the jaw, see there. And see the Gaon Rabbi Chaim David Halevi, zt"l, in Shut Aseh Lecha Rav, Part 9 (Siman 14), who was also asked about this, and he wrote that Maran in the Shulchan Aruch ruled like the Rivan not from the law, even though he wrote generally to forbid. Therefore, this ruling was not accepted throughout Israel, because it was seen as a stringency and not a law, see there. (And so wrote the Gaon Rabbi Mazuz in the journal Or Torah, Tevet 5748, Siman 50) It turns out that the later authorities disagreed on what is the end of the ear according to the Shulchan Aruch: A– the end of the bone, which is approximately the middle of the ear (the Gaon Rabbi Nissim Karelitz, shlita, Shut Tefillah LeMoshe) B– the end of the ear from below where it is connected to the head (Shut Imrei Yosher, notes in Shut Eretz Tzvi. But this is not because until there are the sideburns of the head, as above). C– lower until against the end of the tail (Shut Avnei Yeshfeh, Part 2, Siman 68, Branch 1, in the name of the Gaon Rabbi Yosef Shalom Elyashiv, zt"l, Sefer Pe'at Zekanecha, p. 48). It is clear from these later authorities that the opinion of the Shulchan Aruch suffices until the end of the ear. Can one then rely on these later authorities and act thus until the middle of the ear?

Hello,
Our teacher, the rabbi, instructed that one should not be lenient against the words of the Shulchan Aruch, and it is forbidden above the end of the hard part of the ear. There is room to be stringent until the end of the soft part of the ear.

Shulchan Aruch Yoreh De'ah 181