There is a program called ``mkboot'', now on version 2.0, at:
ftp://ftp.unit.no/pub/NetBSD/contrib/mkboot-2_0.tar.gz

It can be used to make kernel-copy disks, fixit disks, and security disks.
I have used it on several occasions.  It saved my butt.  It uses crunch.
Very easy to use.  If it works for you, it'd be nice if you told me.
If it doesn't work when making the crunched bins, (cd <dir> && make objs)
as there is something wierd about the crunch makefiles.

(PS: This was originally based on someone else's work, namely Hellmuth
 Michaelis and Christos Zoulas...  I will put your names back in in the
 next dist, as I didn't really expect to ``publish'' this tool back when I
 removed that banner)
-- 
email: vax@cs.utexas.edu