can anyone tell me /point to instructions on how I can set up a persistent home under antiX?

I have M7 booting from an ide flash drive, but i'd like to be able to whack in a usb flash to hold the volatile stuff on ala DSL/Puppy ???

Unfortunately you can't (yet). You will have to use the usb as a livecd with aufs to install etc, but it won't save the changes on the next reboot. Or I guess you could try installing antiX to usb stick as if it was a full install. I think this will work, but I haven't tried it.

Also for the livecd on usb stick, you could probably make a separate partition and before you finish the session, put your downloaded files there. On next reboot, you'll have to transfer them back though.