It seems to me that you have a similar need to what Jeff wanted out of his bed bar. He wanted to be able to sling a tarp over it and sleep in the back. He also stated that for those long trip he would possibly need more storage, maybe some sort of basket that he could place up on the horizontal part of his cage, then remove or just move to the bed if he wanted it lower. This is what we came up with for his needs, although its not complete in these pics, as he still needs to add the X bracing up top and the crossbar behind the cab.
http://board.marlincrawler.com/index.php?topic=39009.0As far as where you put your bracing I think it mostly comes down to personal preferance. Anything can happen in the right, or um, wrong curcumstances, so don't expect it to be the thing to save your life, and provide all these other functions as well.
