[exim] virtual user .forward ownership?

I've got everything setup and working in an exim3, spamassassin,
amavisd-new, clamav, pgsql virtual user environment.

I was given the task today of redirecting the spam we get (not dumping)
to a spamdrop in each user's Maildir, now that the bayes is reliable
enough to start trusting it. I've got everything so on my account
(which just happens to have a corresponding shell account) the .forward
loads and works without a hitch... BUT.. In setting that up I noticed
that exim wanted the .forward to be owned by, apparently, ${local_part}
- which poses quite a dilemma since there're only 3 accounts on the
server with shell accounts corresponding to that username.

Is there something I should change in the userforward director to either
ignore this or look for mail.mail ownership? Here's the director:

userforward:
driver = forwardfile
file_transport = address_file
pipe_transport = address_pipe
reply_transport = address_reply
directory_transport = address_directory
no_verify
check_ancestor
user = mail
group = mail
file = .forward
file_directory = ${lookup pgsql{SELECT home FROM users WHERE id =
'${local_part}@${domain}'}}
modemask = 002
filter

Bob..