[J65nko]

I use these permissions, owner and group:

-rwxrw----  1 root  wheel   251 Jan 14 14:31 install.site
-rwxrw----  1 root  wheel  7925 Jan 14 14:31 postinstall_alix

My install.site actually is a wrapper script: that use tee(1) to show the output to console, as well as log to a file.

# cat install.site                                                         
#!/bin/sh
# install.site for alix

INSTALL_LOG=./var/log/post_install.report
install -m 660 /dev/null ${INSTALL_LOG}

. ./postinstall_alix 2>&1 | tee ${INSTALL_LOG}
cat <<END

$0 : done
------------------------------------------------------------
END

I use Makefiles to generate and tar up the siteXX.tgz and siteXX-host..tgz files

sitexx ${SITEXX} :
.if exists(${SITEDIR}/install.site)
        install -p -o root -g wheel -m 760 ${SITEDIR}/install.site FILES 
.else
        @printf "\nWARNING: No  ${SITEDIR}/install.site !!!\n\n"
.endif
.if exists(${SITEDIR}/postinstall_${BOX})
        install -p -o root -g wheel -m 760 ${SITEDIR}/postinstall_${BOX} FILES
.else
        @printf "\nWARNING: No  ${SITEDIR}/postinstall_${BOX} !!\n\n" ;
.endif
        tar cvzf ${SITEXX} ${TARXX}

As you can see I use install(1) to adjust owner, group and permissions before creating the tgz files.