Exhaust plenum for 100mm ducts (parametric model)

For anyone who needs a simple exhaust plenum. I'm working on upgrading my 3D printer ventilation system and needed some bents, ducts and exhaust plenums etc. Figured I might design and print the parts myself. 

Even with the size of these large objects and relative large amounts of filaments, I've come to the conclusion that home supply stores are an absolute ripoff for most (if not all) plastic parts, ducts, bents and whatnot's. 

So, on request, hereby a 3D FreeCAD model + STP file of an outside air plenum which can be used for connecting a duct to an outside air grille. Feel free to use the 3D model and edit this anyway you like.

Since the build volume of my own printer is too small, I cannot test this design unfortunately. However, I expect that it should print without supports. Would like to see makes of this model and let me know if it is OK!