Not so simple.

Common filaments are not strong enough for this, or will melt in the summer.
Advanced materials require advanced printers, and not everyone has them.
Selling 3D printed parts requires full business involvement, in particular, insurance - people whose cargo box flew off and killed a kid on an intersection will probably want to shift responsibility to the place where they got the parts from.

Now, google this: "land rover expedition roof rack thule riser 3d printed" - and Bob's your uncle.

 

I hear you. As an engineer I fully agree with the filaments argument. But don’t have an uncle Bob for the price I think the Thule Caprock kit is going to be my pick with the motion 3 xl. If anyone has actual experience with this set up please chime in.

 

Etrailer said the Thule Caprock riser kit will not fit the expedition rack. Back to square one…

 

I think Etrailer are mistaken and simply stating that it’s not listed as fitting.

 

Etrailer is mistaken, I'd bet a case of beer on that. It fits the standard 20mm T-track which is what the cross bars in the expedition roof rack are, same as the LR cross bars as they are all made by Thule. All my Thule t-track accessories fit my LR roof rack. you could order it from Amazon, get it this week and have 30 days to return it if there is an issue...

 

Ok so I bought the Caprock cargo kit mentioned above. It does fit the rack however it raises the box almost 1.5” above the rack leading to a lot more wing noise. The powrfuluk ones make the box lay flat so less wind resistance.

 

That’s good feedback - thanks for reporting back.

I was shocked actually how quiet my Thule Force L or whatever it’s called box is up there. Really -- it was surprising. On another car of ours that I sold (FU Subaru) it was very very loud)