helpful- indeed, I said much earlier that there were FOUR teshuvos by R’Moshe where he discusses Bat mitzvos and so there are. Look in the ~Jad Moshe” ,an index for the teshuvos, and you will find the other one. I do not have the teshuvos at hand but I checked it over shabbos and there clearly are four teshuvos. The reason this is important is that in that last teshuvo(unmentioned in this thread) ,written in Tof Shin Jud Tet- 1959, I think R’Moshe says that you can have a kiddush for the bas mitzvah in the shul if this is the minhag and the girl can speak at the kiddush.I’ll be happy to double check the source again and tell you which teshuvo it is if I am quoting correctly.
as far as the gemoro in sukkos, I just indicated that the idea of “znius” in its acceptable sense- meaning modest and small- does not apply to chasunos as the meaning of “znius” in that gemoro means something else totally.