Will this work for modded rails?

Not out of the box. Support will need to be manually added per mod, and tested.
If you have a mod you'd like supported, feel free to open a ticket on the
Github Issues
page.

Why don't the diagonals line up with my blueprint?

Diagonal rail spacing isn't as clear and straight forward as grid aligned paths.
There are several ways to approach diagonal rail spacing, and I simply picked
one which I find appealing, and was easy to write the code for.

I Found a bug/edge case/unexpected behavior!

Please post on the
Github Issues
page and I'll take a look. If you can, provide:

• Steps to reproduce.
• Save file (contains undo history).
• Blueprint of the path.