I am doing them right now.
First, read this thread : http://www.jeepforum.com/forum/f37/rear-bumper-w-swingout-tire-carrier-follow-along-101332/
Then, browse this forum section : http://www.jeepforum.com/forum/f37/
And finally, if you want pics or if you want to post pics, go there : http://www.jeepforum.com/forum/f59/
As for my own bumpers, I use 3/16 steel. I am doing the rear one first, with no swing-out for the moment. I may be doing it later, but for now I don't need/want it. Not sure also if I want a bumper mounted carrier.
I do all my cutting by hand. I don't have an angle grinder or sawzall. It takes time but is gives clean cuts and sure makes me proud of my bumper.