I Feel Like My Tefillin Are Too Small.

A customer read that tefillin should be two fingers by two fingers. He measured his tefillin and found that they were slightly less than this measurement.  It just so happens that his tefillin are size 32, the size that I make most tefillin sets that I sell.  I would like to clarify that this measure of two fingers by two fingers is including the titora. Here are the words of the Mishna Berura:
נכון לחוש לדברי הגאונים שאומרים שמלכתחילה לא יעשה אותן קטנים מאצבעיים והיינו עם התיתורא רחב ב’ אצבעיים
“It is proper to take into account the words of the Geonim who say that the battim should preferably not be made smaller than two fingers with the titora.”

This is from the Keses HaSofer, the most important sefer on Stam in the last 200 years.
אורך ורוחב הבתים וגובהן אין להם שיעור וממירים יש לחוש לדברי הגאונים שאומרים שלא לעשות קטנים מרוחב שתי אצבעות עם התיתורא.
The Chasam wouldn’t give smicha to any sofer who didn’t know it well. It says that the titora is included in the two fingers.