This is the teshuva I referenced in the previous post:
For those who didn't read the teshuva - According to Rav Shlomo Zalman: In a case of a mitzva one may walk behind a woman.
I may add that there is still a gemara-Rambam etc. to contend with and to change a halacha b'zman ha-zeh based one one vague source is difficult in my eyes. Not that I am arguing with Rav Shlomo Zalman - I am just adopting the approach of many other poskim. The עיקר is והיה מחניך קדוש!!