Hey, thanks for taking time to reply.
As for the fn_path column, you're right, it's used for order of categories, but in seditio you are adding subcategories like this:
"Intro" path: 02
"Intro - About us" path: 02.01
But since forum_structure is just used for categories, and not forums and subforums, it could be numeric.
So are you suggesting me to drop table and create new INT?