First ignore the name in the frame params.  I use that to get fvwm2 to
give the window a specific icon in my fvwm2 icon manager.  The key is
the if statement.  The message config is used when you do an m in
either the group or summary buffers to generate a new mail.  So if
there's a live summary buffer, I assume I'm in summary mode and I
enforce the summary configuration in the main frame and put the
message buffer in a new one.  If there's no summary, I enforce the
group configuration on the main frame.  Similar for the post
configuration.  For reply, reply-yank, forward and draft I do
essentially the same thing except there's no need to check for summary
mode.  In those cases I force article configuration (except for draft
which is summary) on the main frame and put the message in the new
frame.  Here's reply-yank to illustrate it.