procmail and nnfolder

[jason@mastaler.com (Jason R. Mastaler)]

I'm still trying to find the "right" relationship between Gnus and
procmail.  I currently use procmail to shuffle my incoming mail info
different folders, one mail folder for each mailing list.  So the ding
list goes into ~/Mail/lists/ding for example.  I use Gnus to read
these lists with nnfolder as the backend.  So, my group for the ding
list is 'nnfolder:lists.ding' .  Reading through the Gnus manual today
I noticed in the "Mail and Procmail" section:

  If you use nnfolder or any other backend that store more than a
  single article in each file, you should never have procmail add mails
  to the file that Gnus sees. Instead, procmail should put all
  incoming mail in nnmail-procmail-directory. To arrive at the file
  name to put the incoming mail in, append nnmail-procmail-suffix to
  the group name. The mail backends will read the mail from these
  files. 

So does this mean I've been doing what the manual says not to?  (It
looks like it)  If so, why is this bad?  I've never noticed any side
effects from this combination.  I'm also a bit confused with at the
proposed solution of having procmail filter incoming mail in a 
nnmail-procmail-directory instead.

Here is the included example:

  (setq nnfolder-directory "~/fMail/")
  (setq nnmail-spool-file 'procmail)
  (setq nnmail-procmail-directory "~/incoming/")
  (setq gnus-secondary-select-methods '((nnfolder "")))
  (setq nnmail-procmail-suffix "")

Why are nnfolder-directory and nnmail-procmail-directory two different
directories if nnmail-procmail-directory will contain the mail boxes
that procmail appends to and nnfolder-directory is supposed to be
"All the nnfolder mail boxes will be stored under this directory"?

Is the idea to have Gnus use nnmail-procmail-directory as a temporary
directory that it draws from to process and then deposit nnfolder
mailboxes in the nnfolder-directory?  In this case, I guess I would
have procmail filter like this (for example):

ding list --> ~/incoming/lists/ding
bind list --> ~/incoming/lists/bind

Then, if I define (setq nnfolder-directory "~/Mail/lists/") + 
(setq nnmail-procmail-directory "~/incoming/lists/") would Gnus
automagically know that the group 'nnfolder:lists.ding' should be
drawn from ~/incoming/lists/ding and stored as ~/Mail/lists/ding ?

Thanks,

-- 
Jason R. Mastaler                                 jason@mastaler.com