I guess I like the idea of being able to customize the weight by adding tungsten beads between the stacks and the ability to mix and match head and tail sections. Also, the fly slides out of the way once the fish is hooked. Wonder if the 2 hooks used in gallop patterns result in more hook-ups than the single stinger hook used with tubes.

Did a bit of searching online and didn't find any examples. Most stackable tube flies seem to be of the Intruder variety (ostrich or marabou splayed over balls of dubbing to resemble a monster leech). I guess these would also attract monster browns. I dunno.