good job mang
a suggestion for the box, in my old jeep ( shhhh i know ) i took up the carpet-in your case the rubber to expose the bare steel. took 1 inch thick wood and glued it to the steel floor with some super silcone adhesive that car stereo guys use. then screwed the boxes into the wood. you can pretty much lifth the vehicle by the boxes. if you want to take it out just cutt off the wood and grind off the glue - repaint
just a thought
