It turned out that the CURA version I was running didn’t tell me there was a newer one available, even though I’ve used the update checker. Regardless, version 2.6.1 solves the problem of floating support structure I was facing. Many additions and improvements happened since revision 2.3.1, and the test print went well as well as the support structure dissolution.
A few learning: 1) I will be able to print the design as planned without having to manually add support structures. 2) It will take some serious time to print the final model first, and then clean it even using the water-soluble PVA material. 3) The same model, with almost equivalent slicer settings, yields noticeably different print qualities, with a disadvantage to the newer version.
But I take the latter problem vs. my initial issue at any time. Now that the floating support problem is solved, it is time to start working on the battery holder. Stay tuned.