This is the file in ~/bin/init to replace the standard init script. It will only work if your home/bin directory is before /sbin in the path.
#!/bin/bash
if [ "$1" -eq 7 ] ; then
sudo acpitool -s;
else
if [ "$1" -eq 8 ] ; then
sudo acpitool -S;
else
sudo /sbin/init "$1";
fi
fi
It is setup such that the standard runlevels (0-6) are passed straight back to the /sbin/init script while level 7 is suspend-to-ram and runs
acpitool -s
And runlevel 8 runs suspend-to-hdd
acpitool -S