I too am in the planning stage for mounting three 120WATT size solar panels on my off-road POPUP roof.  
I will want the two front 120WATT panels to have quick disconnects so that I may move them to remote ground locations when necessary to keep in the high sun when I need to.  
My off-road trailer roof may also get overloaded when raising with its electric motor with all three panels already installed on the roof so I may have to mount the two front 120WATT Solar Panels in place after I have the roof raised and locked down...
Your "MAGGIE RACK" idea may work out for me as well...
Thanks for the photos - nice clean layout...
Roy Ken