How do we reconcile this Pasuk, which requires the Tzitz to be placed on a Techeiles thread, with the Pasuk in Shemos (39:31) which requires the Techeiles thread to be placed on the Tzitz; and the next Pasuk, which requires the Tzitz to be placed on Aharon's forehead, with this Pasuk, which requires it to be worn on top of the Mitznefes?
Rashi (citing Zevachim,19b): The hair was visible between the Tzitz and the Mitznefes, 1 in which case the Mitznefes was on top of the Tzitz, whereas the middle thread that went over the Mitznefes rendered the Tzitz on top of the Mitznefes. 2 Regarding the middle thread, the part that threaded through the hole 3 the Torah describes as underneath the Tzitz, and the part that went over the top, as on top of it.
How were the Mitznefes and the Tzitz tied?
Rashi: Refer to 28:37:1:1.
The location of the middle brain (Ramban). The space in between the Tzitz and the Mitznefes was for the Kohen Gadol's Tefilin shel Rosh. The Ramban intimates that the hats of the Kohanim Hedyotim covered their whole heads, in which case, they did not wear Tefilin, in spite of the Gemara in Erchin, 3b, which states that they did (See Rav Chavel's notes on the Ramban).