Sorry Don, Michael, I missed your replies somehow.
Yes, the idea is to merge the mailing lists. Florian and I discussed the idea of having a separate PolySix and MonoPoly group but decided in the end to merge them. There is little traffic on the lists, and there is overlap both in interests / subjects and subscribers. I assume this is the same for the Poly800/EX800 list.
About having subfolders for files per model: that is possible. Sounds like a good idea. I can move those after the fact into the correct place. As far as I can tell, this is not possible for photos (yet?).
So just say the word and we can start the migration. The only requirement is that there is somebody here who can assign moderator rights to a new account from groups.io. Please get in touch with me off-list (yahoo@...) if you want to go ahead.
Ben