We ran an upgrade from 8.3 SP7 to 9.1 in a sandbox. The overall effort wasn't too bad, but there were many "gotchas" identified. You will find that majority of the work is spent fixing validation errors. For us...the version of RC was too new and the 9.1 installer did not allow the upgrade to take place since we were on an "unsupported database". Another gotcha we found was that the installation software could not include any spaces (ie: D:\newscale setup\RCInstall-win-11.0.0.0127) or the JDK install directory could not be located correctly when defining it in the first steps during the validation process. Once we made it passed all the gotchas (there where probably more, but can't remember)...the installation/upgrade went pretty smooth. Note: We have not thoroughly tested after the upgrade, so I cannot speak for any bugs introduced by the install.