> Anyone know what the catch is here?
Scaling up could be limited by the availability of Boron:
> Boron is synthesized entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, so it is a low-abundance element in the Solar System and in the Earth's crust.[12] It constitutes about 0.001 percent by weight of Earth's crust.[13]
> Global proven boron mineral mining reserves exceed one billion metric tonnes, against a yearly production of about four million tonnes