Yalkut Yosef on Women's Head-Covering

The Yalkut Yosef is a Shulhan Arukh-based work of halakha, consisting of the rulings of R. Ovadia Yosef as compiled by his son R. Yitzhak Yosef.  (Wikipedia article)  Here's what he has to say about women's head-covering:


אשה נשואה חייבת על פי הדין לכסות את ראשה, ואין לה לצאת לרה"ר כששערה מגולה. ועל פי הדין מותר לאשה נשואה לילך בביתה בגילוי ראש (כשאין שם אנשים זרים), אבל ראוי מאד לנהוג שלא לילך גם בבית בגילוי ראש.    [אוצר דינים מהדו"ק עמוד שנט

ט פשט המנהג שבנות רווקות הולכות בגילוי ראש ברשות הרבים, שמעיקר ההלכה אשה שאינה נשואה אינה חייבת בכיסוי ראש. ורק בעת שמתפללות או מברכות ומזכירות שם שמים, תכסנה ראשן. [אוצר דינים מהדו"ק עמוד שסא. יביע אומר ח"ד אהע"ז סי' ג'. וחלק ה' סימן ה אות ב]

8. A married woman is obligated by law to cover her head, and she should not go out into the public domain with her hair uncovered.  According to law, it is permitted for a married woman to walk in her house with an uncovered head (when there are no unrelated men present), but it is very appropriate to also not go about with an uncovered head at home as well.  


9. The tradition spread that unmarried girls go with an uncovered head in the public domain, as from the essence of the law, an unmarried woman is not obligated in head-covering.  And only at the time when they pray or make brachot or say the name of God, they should cover their head.  


In his view, married women should always have their head and hair covered when men can see it- and preferably, pretty much always, even when there aren't unrelated men around.  Unmarried women seem to have no need to cover their hair at any point (I think- it seems a little unclear, honestly, given how consistently the covering of hair and head are not really distinguished), but should cover their head for the full range of prayer/blessings and presumably for study as well (which I want to find implied in "say the name of God", although it is certainly isn't explicit- do you think that's a reasonable interpretation?).  In other words, unmarried women should cover their head in the same way that I began wearing kippot- for religious behaviors.  I wonder how much this is halakha is followed in practice...