Here is a collection of PDB files and simple shell scripts (some editing might be required) to superpose some "difficult" or "interesting" pairs of structures from the literature:

You can build Kpax databases of CATH and SCOP using these files (some editing required):

Here are 213 "representative" structures of CATH domain families having 10 or more members:

Please note: databases built by different versions of Kpax are generally not compatible. If you download a new version of Kpax, you should re-build your databases using the new version.