Awesome Kees, thanks for doing the experiment!
CMC gum is an oft overlooked material I feel, and here you've shown that it has potential for printing processes. It's cheaper than dirt and fairly easy to work with. It doesn't set like gelatin, which is both a good thing when you consider you don't need heat, and a bad thing when you realize it has to dry flat.
Thanks too for clarifying the PVA issue.