You might also find that if you cut a stone with a much higher RI that the design, you should get a lot more dispersion than expected. For example with the novice stone design having an RI of 1.52, if you cut it in CZ with an RI of 2.15 to 2.18 you will end up with a very spectacular stone.
Unfortunately it doesn’t work the other way around. If you cut a stone with a low RI using a design with a high RI, you will end up with major windowing or a dead center.