Simulations were done first with TracePro before switching to Blender's Cycles rendering engine. After that, a tablesaw and a nerve wracking afternoon of cutting polycarb and acrylic later, we get our options for light tube geometry.

Unfortunately, iPhone cameras have a tendency of compositing images which removes the fine gradients created by the different geometries. Try spotting the differences below if you can! Otherwise, you'll have to trust me that there's some differences.