Hey Fungi

To be honest with you, i dont think it will be possible to print 4x4, because you have to calculate a bit space between the parts. My suggestion would be printing 3 X 3 X 6 which means only 54. But if you align the parts clever, maybe more will fit in.

About the Sandblaster, its just a very easy way to clean the parts. It works really well when using the powder itself to sandblast, as it doesn't damage the prints but its absolutely not necessary to sandblast the parts as the surface finish is good from the beginning.

If you have any more questions feel free to ask