... consider a transfer-lite option that only transfers membershipI think Mark could do that for you if you request it in the "Go" message you send to the transfer agent. But I think that Mark is also right to assume that most groups would prefer to copy over as much of their content as practical.
Are you suggesting adding some additional wording in the instructions for Step 2 to make that option clearer? Or something else?
In Step 3 (arguably too late) the instructions do say:
"In addition to your member list, we will download your existing group
messages and add them to your Groups.io group. Unfortunately, we are
not able to include any attachments from the messages. If you do not
wish to have your existing group messages transferred, simply say so in
your email to email@example.com."
... I would have been perfectly happy if only the membership list withA problem with deferring the copy of messages is that the copied messages are assigned message numbers as they copy over. Which means they would be mingled with new messages if your group members were actively posting before or during the copy. Granted that's better than not getting the archive at all, but I think a lot of groups would find that very confusing.
I grabbed 17+ years of messages with PG Offline in a torturous 24-hourThen you also have (or could have) the the membership list in PG Offline's database, exportable as CSV I think. From that it would be relatively simple to copy/paste the list into Groups.io's Direct Add feature (assuming you bump to a premium group, which you can do for one month only).
In the meantime, our membership is pleased, and we are laying outYou can't remove people's Yahoo accounts, only their membership in your particular group(s). What form of "attack" are you concerned with?
If it is spamming, you can set the group's sections so that only moderators can "Edit" (includes posting new content). Then I suggest not bothering to remove the memberships, just leave the group there as a standing archive of itself.