Thanks. It is somewhat working now, but you are right that there may be some more issues.
I am using RC3 and now went back to the "normal" plugin (not beta), copied the script in the respective folder, and did the edit with sed a specified here.
I started a preclear with 3 cycles. The first time, it started running, but after 2 days (and around 50% progress), it just showed the disk again with the option to "start preclear". I started the preclear process again and it now shows 97% after 52 hours. But this is still the first cycle, so I anticipated preclearing will be completed in a week. I will keep everyone updated whether the preclear cycles indeed complete.