There are a few designs floating around of comet racks. From what I see there are pros and cons to each design. The need for comet racks presented itself to me and my pyro partner last year, so I thought carefully about how I would design the "racks" The main problems I observed wanted to address were:
Depending on where you harvest your comets from the tubes are can all vary in diameter. This automatically makes designing a rack; that is an object intended to contain and direct other objects, very difficult. Not to mention this factor makes a mortar/tube style rack impractical. Ultimately necessitating the design be flexible to accommodate device variance while maintaining strict control over direction/angle. All the while I wanted to keep the design fairly simple, lightweight and portable.
I admired the simplicity of catfish's design, and felt his design was on the right track for my needs. But I wanted something bit more precise and would need to be duplicated many times. The following is what I came up with: