After thinking about this, I wonder if it might be better to make the font include only the custom characters (That is, not include "a", "b", "c", "d", etc.).
That would let the non-custom characters automatically fall back to the regular fault.
If not, I can just apply it to certain column π
Also, are you familiar with how to use the browser's developer tools to redirect the font file to one on your computer, so that you can easily experiment with new versions of the file?