hm, maybe the users could be asked to give it in the form
Code:
!authforums mail@host.com
username could be assumed as playername, allthough there will be sure issues with special caracters ^^
then use the phpbb registration scripts to sign him up with random key, sent in activation mail.
so were sure and we have a playerid for the username.
aditionally, its much more save against them spambots then any captcha or math test
an aditional column with player id in phpbb users could show the xlr content relative easy in playerprofile.