Outstanding work! I've participated in the challenge, but didn't get far. One of the questions I had at the time was - if I'm going to use ML to detect ink, could it invent hallucinated letters, or even parts of text, and how to prevent that?
A stable base corpus and some dynamic programming will allow you to clean up the remainder[0].
[1] https://www.dkriesel.com/en/blog/2013/0802_xerox-workcentres...