Exactly. I was about to suggest the same thing and then saw this post. Or you could just get one long piece of flat bar from lowes and drill the holes where you want for all the lights...

 

I think the last two options mentioned were great if you don't have a welder or know someone who does, the only thing i would worry about is the bolts may loosen up a bit with the bumps if off roading.
Also your light would be mounted upside down so your bolt would be visible and look tacky, and remember the heat that will come off those lights if on for long periods of time could f up your paint.