Tower of Art

I have 'a few' 17/18ml dropper style paint bottles from Army Painter, Vallejo, Reaper MSP and others, and needed a way to store them that didn't take up too much space on my desk, or floor... I also happened to find a carboard tube of the type used when casting concrete pillars.
The tube has an innder diameter of 150mm, and 4mm wall thickness, so I based this project off of those measurements. (You will be able to use other sizes when I finish parameterizing everything)
The trays are stackabl