I don't really know anything about upstart, but it seems that the scripts are also on /etc/init.d:
However, the correct way of changing this sort of thing often is not just creating a script and placing it there, it has to be "installed" through some command. On sysv (debian and some others) it is "update-rc.d", on upstart I don't know. But this link I gave seems to have these instructions.
These files you've listed, if/when they exist, they may be used at some later point on the startup anyway. But there will be quite a bit of stuff that happens before these are executed, if/when they are.