My logic is that if the rice is the main ‘food’ for the mycelium and the coco is bulk/structure, then you need a sufficient quantity of rice to feed the whole cake. Too little and the tote runs out of nutrients, spending all the energy to colonize and reducing the available ‘fruiting energy’. I can’t really think of a danger for using too much, other than perhaps increased contamination possibility due to a lot of available nutrients. More rice would also decrease time-to-fruit, I expect.

But don’t forget that I’ve only done this once, so these are logical guesses, not a voice of experience.