I've downloaded the Fabric 1.21.1 version 2.41a of Tectonic, but I can't find the config file mentioned in the README in order to update the increased_height variable, etc. I've read from other issues that the file is called tectonic.json, but I've searched through the JAR file and cannot find such a JSON file. I've also performed a string search for increased_height and found references in the Java class files and the pack.mcmeta file, but nowhere where I could change the value from true to false.

Where should I be looking to change this setting?

Nevermind. Finally solved it. For anyone else who's silly like me, the mod config file tectonic.json is found in the AppData folder under .minecraft > config or for Modrinth installs Modrinth > profiles > [your_profile_name] > config.

Sorry for wasting time. Hopefully this helps someone else.