As a test I simply inserted a line into the phpBB_users sql table, I added the user name, user id number, email address and copied and pasted the password from the backup sql and it works. I set up an unknown user using my copied and pasted password and it worked. I even did a test ad upload and that worked. So long story short its possible to manually ad the users to the data base. I also tested the unknown user on phpBB and there is no problem posting topics.
I have a bit more work to do to import the existing ads but that should not be a problem. I will update with the progress tomorrow as bed time is calling.