I was thinking about those system-wide files user opinions/advices. @stgatilov said tdm is designed by user-only. But When someone shares his/her system with someone else, that someone get all his configs, missions and mission safes. (When that folder is writeable). And you get that write permissions problem.  How about writing some dynamic/writeable files somewhere else. For example, placing/writing only the fm&fm save folders, inside the user profile folder. Its a standa