borrowing from your method...

install.ftp for preinit should be this:

quote site rw
cd /
quote mkd programs0
quote mkd programs1
cd /bin
bin
put empeg-preinit hijack
quote site chmod 755 hijack
quote site ro
quit

i keep a base.tar.gz in my /programs0 dir, and have the M99firstrun script in /programs0/preinit.d which consists of:

if [ -s /firstrun ]; then
echo "base.tar.gz already applied"
else
rw
cd /
tar zxvf /programs0/base.tar.gz
ro
reboot -f
fi

firstrun is a file in base.tar.gz of course.