Extended heads of the letters shatnez getz

What is the law in regard to the heads of zayin or nun that are extended?

[The pictures are edited, and may be exagerated in order to emphasis the problem]

MS (ois nun) writes: one should be careful not to extend the head of the nun, because it resembles a beis. It seems he is saying so, even if the moshav is short, still an extended head resembles partialy a beis. This follows what the MB 36:3 writes that there are opinions that changing a letter so part of it resembles a different letter is pasul, but the MB there concludes this isn't pasul. So we may understand here the same, that lachatchila this should not be done, bdieved it is not pasul.

The Mikdash M'at (nun:5, in name of Da'as Kedoshim) questions maybe an extended head and short moshav is pasul, because it looks like an upside down nun. (this reason is questionable, why can't a tinok be asked?)

And indeed in Shavet Halevi vol 5:6 writes that if the head is 3k wide it is pasul, either because of resembling a beis or an upside down nun. Accordingly Biur Hasofer (p. 76) writes that if the head is less than 3k wide it may be a shaylas tinok at most.
One must add that the reasons given above, fit to a nun that the head is extended left and not extended to its right, then it resembles a beis or nun hafucha. but if it is extended on both sides equaly [as the first nun in picture] it shouldnt be a problem.

Rabbi Shtern in his Yalkut Hasofer (p. 53) a zayin that the head is close to the length of a dalet is chashash pasul (although the foot is centered). It seems [from his words] that if is 3k long it is definitly pasul, in regard to less he is choshesh.
This pasul in zayin may be proven from the Tikun Tfilins shita (see "Definition of ches - Rabenu Tam") that if the zayins of the ches are extended the ches is pasul, kal vachomer if the zayin itself is extended.

In regard to the left heads of ayin or zadi if they are extended, the Yalkut Hasofer (p. 80) writes they are kosher.

A question may be posed against this – from the Baruch Sh'amar (p. 162) that if a word as matzos or nosen was written malei vav, and the vav must be erased, he is in doubt if this could be fixed by extending the moshav of these letters. Because maybe the letters that have to be close to each other are at the heads level (at the sirtut) and not the moshav part. But, why can't he extend (b'shaas hadchak) the head of nun or zadi to fill in this vacancy, this seems to prove that extending these heads are pasul and won't save the tefilin.

This Baruch Sh'amar is quoted by BY and Magen Avraham 32:33 and all later acharonim.

I understand from the Baruch Sh'amar that all the heads of shatnez getz may not be extended (and not because some of them may resemble other letters, as the nun and zayin) but this is not a rosh of the letter, it has changed its form to a gag.

The thin letters have a head (rosh) and other letters as beis, dalet, hai, etc. have a gag, and these features may not be changed.