It works for me.

I decided to go ahead and download that"updated" version of the ISO, and then went through all the antix2usb official steps. I used the ext3 filesystem. And.... using the PLOP CD/USB stick combo works. I don't understand why. I've tested it, it seems to be persistent.

I do have questions, though. For example, when antix starts up, it doesn't ask for a user name and password, it automatically starts as demo. Is that the intent? How do I set up other users, and have it ask me for the username and password?

That is the intent. There is in Control Centre -> System -> Manage Usrs which will set up a user, but I'm not sure if it will persist. I very much doubt it. You can edit /etc/slim.conf and change the yes in autologin to no. Again, not sure if it will work.

Just an FYI:

I tried what you suggested. It appears to work fine. I set up the new user, when I login it asks for my user name and the password, and it appears that everything I do as each user is separately persistent.

Thanks.