Ah, but in this case it's trivial to make them commensurate, since you can add any arbitrary amount of vacuum around the nanotube. It's when you have two crystalline electrodes (with different periodicities in X/Y) that it becomes more difficult. It's easy to make a nanotube/nanotube junction, or a metal/nanotube (or metal/molecule/nanotube) system, but metal1/molecule/metal2, that's more tricky.