INTLLAB Vortex Mixer Adapter

I purchased the INTLLAB vortex mixer to mix the paints I use for my miniatures. The shape of the mixer's top plate works well if you mix your paints cap-down, but it's hard to keep the bottles in place when they are upright. 

I've experimented with mixing paints in both orientations using clear bottles filled with gloss varnish and a small amount of transparent pigment to get a clear view of what's happening inside the bottles. When mixing cap-up, a strong vortex is formed inside the bottle and the paint mixed quickly and thoroughly. When mixing cap-down, the paint is vigorously agitated, but I could not get a vortex to form. The paint does mix, but not as quickly or completely. 

After discovering that mixing cap-up is best, I designed this cup to make it easier to keep the bottles in place. Just print it out with supports, or without if your printer can handle bridging. I printed it in TPU and PLA and they both work fine. 

The cup tends to fly away if you remove the bottle while the mixer is still spinning, but I found that placing a small amount of poster-tack or some other sticky substance under the cup will keep it in place.