Nice job.
I need to do something like that as I need to drill holes in the bottom of my bumper - where the existing sewer hose storage is - so that I can attach a "skirt" so I don't get rocks and dirt on my toad.
But when I attach screws to the bottom of the bumper, it won't allow me to put the sewer hose in there anymore.
And one other project I am planning is the installation of a set of hydraulic levelers - which I have to do first so that I don't put the sewer hose storage tube in the way of the leveler pistons.
I love to see people doing RV projects.