Sources from contemporary Poskim that minhag hamakom does not make a difference (in terms of “shok” and “z’roah” and hair with the exception of Krias Shema with hair):
1. Yabia Omer 6, Orach Chaim Siman 14, letter 3: “Haholchos b’gilui zroos overes al hadin, v’af al pi sheze darchan k’sil lamo, pshita sheasur l’kros krias Shaema u’l’varech k’negdan… ain l’hakel bazeh klal. u’cvar casav haGaon m’Lubavitch: ha’im nomar sh’im yirtzu hanashim lnhog laleches bimos hakayitz b’shuk meguleh, sh’ail bazeh mishum shuk b’isha ervah, m’pna shenahagu cach? yishtaka hadavar v’lo yomar, vadai, kaivan shehu ervah, lo moil mihhag bazeh”
“Those who walk around with revealed arms are transgressing the law, and even though this is their usual foolish way, it is obvious that it is forbidden to say krias shema and to make brachos in front of them.. and one is not allowed to be lenient in this matter. And the Lubavitcher Rebbe (The Tzemach Tzedek, grandson of the Tanya) already wrote: Would we say that if women want to walk around in the summer with uncovered “shok” (upper leg) that it is not included in “shok b’isha erva” since they are accustomed to do so? We can certainly not say such a thing. SINCE IT IS ERVAH, THE MINHAG (CUSTOM) DOES NOT HELP”.
2. Igros Moshe, Orach Chaim 1, Simanim 42,43:
“rak b’searos megulos, shenispartzu b’davar rov hanashim b’avonoseinu harabim, ain l’esor l’kros krias Shema k’negdan m’taam shecasav Aruch HaShulchan, shekaivan shenispartzu b’davar harbei nashim, af sheovros issur, ail din ervah lkrias Shema u’l’divrei Torah..aval im nireh bsaral b’makom shetzarich lihiyos mechuseh, af sheholchos megulos mitzad pritzus, yesh l’esor m’lkros Krias Shema v’amiras Davar Torah k’negdan.”
“Only with uncovered hair, which has become widespread amongst most women due to our many sins, we can’t forbid the recitation of Krias Shema in front of them for the reason given by the Aruch HaShulchan, that since it has become common amongst many women, even though THEY ARE COMMITTING A SIN, it is not ervah regarding the recitation of Krias Shema and Divrei Torah… but if their skin shows in places that it is supposed to be covered, EVEN THOUGH IT IS THE NORM TO WALK AROUND THAT WAY BECAUSE OF PRITZUS, it is still forbidden to recite Krias Shema or to say Divrei Torah in front of them.”
We see the following from these sources:
1. In terms of hair, upper arms and upper legs, the “minhag hamakom” makes no difference in terms of its being forbidden to walk around that way.
2. The only situation in which one of these things becomes more lenient due to minhag hamakom is for saying Krias Shema or Divrei Torah in front of a woman with uncovered hair. However, even in terms of uncovered hair, it is still forbidden to walk around that way.
3. These halachos are not just about a man saying krias Shema in front of a woman. It is also forbidden for a woman to walk around with these areas uncovered even if no one is saying Krias Shema.
4. The halachos of Krias Shema are actually more lenient (I think DY may have pointed this out earlier).