Asymmetry of R. Meir's times to inspect tzara'at (Nega'im 2:2)

Question

Nega'im 2:2:

אֵין רוֹאִים הַנְּגָעִים בַּשַּׁחֲרִית וּבֵין הָעַרְבַּיִם, וְלֹא בְתוֹךְ הַבַּיִת, וְלֹא בַיּוֹם הַמְעֻנָּן, לְפִי שֶׁהַכֵּהָה נִרְאֵית עַזָּה. וְלֹא בַצָּהֳרַיִם, לְפִי שֶׁעַזָּה נִרְאֵית כֵּהָה. אֵימָתַי רוֹאִין. בְּשָׁלשׁ, בְּאַרְבַּע, וּבְחָמֵשׁ, וּבְשֶׁבַע, וּבִשְׁמֹנֶה, וּבְתֵשַׁע, דִּבְרֵי רַבִּי מֵאִיר. רַבִּי יְהוּדָה אוֹמֵר, בְּאַרְבַּע, בְּחָמֵשׁ, בִּשְׁמֹנֶה, וּבְתֵשַׁע:‏

One may not examine Negaim [to check them] in the morning or towards evening, and not inside the house and not on the cloudy day, because the dull [Nega] seems bright [in these circumstances]. And [one may not examine] at noon, because the bright [Nega] seems dull. When does one examine? During the third, fourth, fifth, seventh, eighth and ninth [hours of the day]. These are the words of Rabbi Meir. Rabbi Yehudah says: During the fourth, fifth, eighth and ninth.

Now, R. Yehuda's opinion seems reasonable. The first three hours of the day are too dark, the next two hours are fine, and the final hour before noon is too bright. This is then reversed in the afternoon: the first hour after noon is too bright, the next two are ok, and the final three again too dark.

But I fail to understand the logic of R. Meir, who seems to have an asymmetry between morning and afternoon. According to him, the first two hours of the day are too dark, the next three are ok, and the final hour before noon is too bright. But in the afternoon, immediately after noon one can start to inspect for three hours, and the final three hours of the day are too dark.

How can we understand R. Meir' opinion?

Answer 1

See the nusach of the Rabenu Shimshon following the Torat Kohanim.

אימתי רואין בשלש שעות ובארבע ובחמש ובשש ובשבע ובשמנה ובתשע דברי ר"מ

Can be this makes sense.

The Melechet Shelomo says that the beginning of the Mishna that excludes midday follows the opinion of Rabbi Yehuda and Rabbi Yose, the last is in torat Kohanim, not in Mishna.

But in torat Kohanim there is an asymmetry in Rabbi Yose hours and the Melechet Shelomo explains that according to Rabbi Yose, there are three hours of high light, 6-7-8.. and he permitted to verify negayim around those three hours, that is 4_5 & 8-10. Why the eighth hour is more luminous than the fifth, I don't know, perhaps generally there are more clouds in morning. The interesting issue is that according to the opinion of Rabbi Meir following the version of our Mishnayot, it's inverted, morning is more enlighted than afternoon. So, as @Heshy suggested maybe that those opinions are geographically dependent, following the place of mountains.