It is a special case, but in the case of stud*.dat, any time you find a file of the same name, but with the d replaced by a 2, the "2" file is guaranteed to be a lower-quality version of the same file. This is a requirement of the library, as far as I know. So, there isn't a hard-code list, simply a check of: Is this a primitive with a filename that starts with "stud"? If so, is there an "stu2" version of the same primitive? If so, that's a guaranteed lower-quality drop-in replacement. (Lower quality in this case means 8-facet circle instead of 16-facet circle.)