Worked on the generator access this weekend.  The genny was too tall to fit underneath so it is 1/2 in and 1/2 out. Layout dictated the location on the truck. It will be bolted to a shelf that slides in and out on a 500lb drawer slide.  Hinge will be in the front edge of the hole, not the top.  Framed the sides in with steel angle, you will see some of it in the picture but it’s not done.  Will box in the area under truck to keep it clean.  Will spray with bedliner as well.
 
Theory of operation will be to pull into location, open door and secure.  Run Genny.  If space allows, slide the genny out so it is completely free air.  Will probably install a 120v fan as well to keep her cool.