Cannot change font size in visual.TextBox

Hi everyone!
I am very new to Psychopy and I’m writing code for a P300 speller experiment setup.

In this experiment I have a matrix 6x6 of alphanumeric characters, and with very precise timing I need each row or column to be highlighted exactly once in every run. I manage to make the col or row blink for now (using the TextBox class as it performs way better than stimtext for submillisecond timing).

However, one thing I was not able to do (and which is possibile with stim text) is change the font size inside the textbox. I looked up every API I could find in the class and even the source code itself, but found nothing about changing font size. Is there any way to do it?

Thanks in advance!