Okay, I'm calling it a day with this skill. I probably still need a few things from time traveling, but I have created three plumbots and reached level 10 in the self-employed inventer profession. I think VJ and I have done well. Time to try something else!
I hope the thread stays open in case others would like to give it a go. It's not fraught with frustrations like some other professions. Sculpting is fun too!