Garrett,
Are you trying to adjust the length of the control arm, or just tighten the bolt that holds it to the frame?
In any event, Bob is right, there isn't much of an issue of the axle shifting, just don't adjust the axle height once it is disconnected. Basically, you can jack up the vehicle a little bit, and then block the wheel. Disconnect the front end of the control arm and you are good to go. It's harder to put the control arm back in if the axle height has been moved with the control arm off. The good news, is that the bolt is cone shaped and you can use a hammer to get it started if it doesn't just glide in.
Does this make sense? PM me if you need installation instructions for the control arms.
How is the rest of the system working for you? Did you get the lights installed?