4 inch Dryer Vent Duct Inset Cover

My goal is to create a Dryer Vent Cover that would fit INSIDE the ventilation duct. The building contractors ran the ducts in the corner of my deck floor joists meaning I could not install a cover to the outside of the vent without cutting it on three sides. I could not find a viable commercial product so I bought a printer and started learning CAD. 

It is unfortunate that the ductwork on my house was done so poorly, as the ends of the duct are completed destroyed and smashed. This means my prints perfect round stepped walls will not fit MY duct in any meaningful way. This should fit undamaged new ~4" ductwork, especially with some heavy silicone caulk application.

I recommend printing in something that is both weather resistant and UV resistant like PETG if used outdoors. Perhaps a coat of flex seal or paint would be good too durability. 

I will be remixing this with several revisions to fit my oddly shaped and damaged dryer duct and as well as my basement bathroom duct which is supposed to fit 3" ducts and has a similar trauma. I need to thicken the grid walls as well.