How’s the weight of it when the phone isn’t docked? Perhaps you could add an insert for a steel plate on the bottom so it has a nice feel when the phone isn’t docked?
It's not a lot, because I printed it with an infill of 10%. You can increase it, and make it around 40% or 50%. Some people also use sands to make it heavy. For now it doesn't bother me and I think because I'm putting other things on top of the tray, it doesn't move around easily.
It can be a bit painful to get hold of, but I’ve been experimenting with micro-suction sheets, which allows you to “stick” things down to smooth surfaces, without adhesives (the material surface is full of tiny pores that act as millions of mini suctions cups). And allows you to easily remove, and re-stick them later without leaving any goop behind.
It’s a nice way to stop these types of 3D prints from sliding around in surfaces, without having to resort to weights or lead shot, which it way more painful to integrate that you would expect.
