Some versions of the RipGuard protection, DVD Decrypter can handle without problems. But your method is very time consuming. To skip the sectors that can't be read can take 7-8 hours. If you only had a couple of read errors, that would to me indicate that the source disc was scratched or dirty and it was not a genuine protection that you defeated with your method.

Creating a PSL file based on given errors at cell range would speed the process up dramatically.