How to create custom 41C modules from keystroke programs?

[Dave Britten]

Now that I've got my DM41X, I have a clear use case for being able to create my own module ROM images to "plug in". I only do standard keystroke programming - no synthetics or ML stuff yet. What's the most painless way to take keystroke programs and turn them into module ROMs? Are there any restrictions or limitations on what such a module can do, such as calling functions that are located in other modules?