truncating body of long msg

Hi all,

I am saving a copy of incoming msgs in another mailbox just to be sure. To
save this from bombing out the quota, I'd like to truncate the body of
large msgs to a few lines (these usually contain more or less useless
attachments). My recipe however does not want to truncate the body
(it works for the header, i.e. replacing b with h):

:0 c
{
  :0:
  * < 204800
  mbox
  
  :0 Efbw
  | head -5
  :0 A:
  mbox2      # this always saves the full body :-(
}

What am I doing wrong? There must be a trick to it? Even the latest
3.13.1 doesn't work any different.

Thanks,

Volker