B'nos Tz'lofchod

Last Shabbos, my friend David F. asked me how I understood the dikduk of the following passuk (Bamidbar 36:6):

זֶה הַדָּבָר אֲשֶׁר-צִוָּה יְהוָה, לִבְנוֹת צְלָפְחָד לֵאמֹר, לַטּוֹב בְּעֵינֵיהֶם, תִּהְיֶינָה לְנָשִׁים: אַךְ, לְמִשְׁפַּחַת מַטֵּה אֲבִיהֶם--תִּהְיֶינָה לְנָשִׁים.

"This is the matter which HaShem has commanded regarding the daughters of Tz'lofchod, saying: Let them be married to whom they think best; only into the family of the tribe of their father shall they be married".

The issue that he brought up was how the verse uses the masculine possessive term "בְּעֵינֵיהֶם" to refer to the b'nos Tz'lofchod.

Shortly before, I had been browsing through the Oznayim LaTorah, and noted that he also asked this question, answering regarding the importance of not relying too much on one's own opinion in deciding on a proper shidduch, as strong feelings of love can blind one towards problems that a third party would see. Even though the b'nos Tz'lofchod did not have a father, nor brothers, they should still seek out the advice of others before making their decision. This idea is expressed by the usage of the masculine term, rather than the feminine one. ad can tamzis d'varav.

Even if one uses the answer of the Oznayim LaTorah, though, one still can ask about the usage of the masculine term "אֲבִיהֶם" at the end of the verse. The simple answer that I wanted to give is that the Torah doesn't always care about proper grammar. We also see masculine pronouns used to refer to the B'nos Tz'lofchod in 27:7:

כֵּן, בְּנוֹת צְלָפְחָד דֹּבְרֹת--נָתֹן תִּתֵּן לָהֶם אֲחֻזַּת נַחֲלָה, בְּתוֹךְ אֲחֵי אֲבִיהֶם; וְהַעֲבַרְתָּ אֶת-נַחֲלַת אֲבִיהֶן, לָהֶן.

"The daughters of Tz'lofchod speak right; you shall surely give them a possession of an inheritance amongst their father's brothers, and you shall pass on the inheritance of their father to them.

This verse is particularly interesting in that it starts out with the masculine "לָהֶם" and "אֲבִיהֶם", but then changes over to the feminine "אֲבִיהֶן" and "לָהֶן". As a further data point, the nun at the end of the word "מִשְׁפָּטָן" in 27:5 is written large, which may or may not have significance to the discussion at hand.