Three more examples of where I believe R. Falk’s book veers off the halachic path into the area of personal opinion.
1)He discourages very long skirts. Obviously these are more tzniusdik, rather than less, but he happens not to like that look, so he finds some problem with it.
2) He discourages denim skirts. I wonder where in Shulchan Oruch that is mentioned, since it wasn’t around then. In addition, it is one of the most opaque and least clingy materials, possibly giving it an actual advantage in tznius.
3) He sets limits in how much or how big jewelry one can wear. He is then faced with a problem that frum sephardic women have always worn huge amounts of very large sized jewelry and ornamentation. He says in response that for sephardim it is fine since that is the norm. Now, as far as I know, sephardim have the same halachas as ashkenazim, except where the Rama argues with the Mechaber. I am not aware of any such machlokes on this topic. The bottom line, whatever you and your family feel is right for you and are comfortable with is OK.
How can an author interject personal opinion into a halacha sefer? Note, even if there is a source from some aggadta on this or that point, the halacha does not follow every obscure aggadta. Only halachic gemaras which are brought in shulchan oruch are binding.
Of course one can be as machmir as one wishes. The problem is that when chumras are taught as halacha it causes people to look down on others, and violate onaas devarim and loshon hara which are far far more severe violations. In addition, it stifles people from doing what is comfortable to them and makes them start hating the religion. Chumras are one’s own personal business and should be kept private. In fact, there is a halacha that if one takes it upon himself a private fast day, and tells anybody about it, it is a terrible aveira, and shows it is only for kavod.