Yes, I like the idea of using ducts, but it does add a bit of complexity and mass. I think lightweight fiberglass ducts would be a great idea on a future project. Ducts on EDF aircraft like scale fighter jets are commonly used.there are a lot better fans out there. Also could have used NACA ducts for the inlets.
Not sure about better fans. I know there are lots of manufacturers and suppliers of EDF's for RC aircraft. I needed something that was relatively cheap and easily available. I chose these because they were in stock on Amazon and after testing the first one, they preformed as advertised. Please keep in mind that I also have several other projects using EDF's and I've purchased a bunch of them - more than 10 now, along with ESC's and batteries.