I have a large RUBBERMAID chest across the front of my truck bed. I also have the FOLD-A-COVER hard plastic bed cover and the front bed opening is just the right size to fit the rubbermaid box.
I can open the front fold-a-cover and then open the Rubbermaid chest lid...

Of course the Rubbermaid chest is not a secure unit when locked but the fold-a-cover I am using is... Everything out-of-sight is the best way to have it.
The fold-a-cover will work with your pictured setup shown in your post. Will cover all the tool boxes and fifth wheel hitch when you are unhooked. It will fold up on top of your front tool box when you are hooked up using the fifth wheel hitch and will probably be a problem getting into the front tool chest when pulling the trailer...
This is how the FOLD-A-COVER G4 ELITE looks on the F150 Ford Extended cab...

I pulled a fifth wheel for a few hundred miles and decided I didnt have a truck big enough to tow it so my fifth wheel sits in my CAMP BACK YARD now.
Those diamond plated tool boxes are expensive but worth it for security purposes.
Roy Ken