I have uploaded version 0.2a6 of this tool. This version only changes one thing, but it was a serious enough bug to warrant a new version of its own.
Seems like the RIM specification was incorrect as to where certain data was stored, which caused the game to have trouble loading RIM files written by this tool (though KotorTool had no problems loading them). This should now be fixed, and as far as I have been able to verify the game properly reads the content of modified/new RIM files now. (Lesson learned: don't rely on other tools to verify that your own utilities work.
Download link is in the first post in this thread.