My reading of these printers was so demoralizing that I originally planned to sell them in as-new condition and take a loss.
So you haven't even tried printing anything ?

You do know that a lot of negative 3d printer reviews are down to the general incompetence of the end user and often nothing to do with the machines themselves.

It seems weird to me that you're spending money on a vat lining BEFORE printing something without one.
You might not need one :-)
How can you know unless you try ?