Batteries maybe? Lol, I'm assuming they are referring to a better transfer of energy (looks like these shafts have more mass, but could be wrong).
There's also potential energy, but I won't pretend to know what I'm talking about here. The OP asked if you could add material to lengthen a shaft, and i think the question has been answered. Just curious to hear from Ferelz about why Mezz makes a bad product.
I'm always open to learn about the physics behind how this stuff works, and hopefully more knowledgeable people can chime in. That's how science works, you have to provide evidence to support a claim, you can't simply say "No, this answer is wrong because I don't like it..."
Joey, you've had some interesting opinions on deflection and such. Do you have any thoughts on this?