Ubuntu :: Starting X Automatically In A Minimal Install?

I'm moving a homebrew arcade cabinet I have in my sitting room over from Gentoo to Ubuntu. Gentoo's served me well for a couple of years, but it refuses to recognise a touchscreen I recently installed on the cab, so I thought I'd give Ubuntu a try.

There is very little space on the SATA DOM inside the board in the cab, so I try and put as little OS on there as possible. To that end, I installed the minimal iso, and then apt-got X. I manually configured xorg.conf to make both monitors attached to the cab work, and I can enter X fine from the command line.

But what I need to do is have X start on powerup and automatically run my game. In Gentoo this is as simple as putting "xinit [GAME]" into /etc/init.d/local.start (the equivalent of rc.local). No login required, the prompt didn't even come up until I'd exited the game.

However, if I try and do this in Ubuntu, X can't find any devices, even though rc.local is at position 99. I've tried putting the lines in rc.local as well as manually update-rc.d-ing my own files, but no luck. X refuses to start until after the login.

So what seem to need is some way of automatically logging in as root on the command line, starting X, then running my game.