The only large hole should be the one you need to run the wires and cables through. Other than there there should be no large holes.
net with large holes
Reuters
up to 5 ft in diameter
The size of the holes in a sieve depends on what is the the size of material to be allowed through the holes. A set of sieves (flour sieves, garden riddles, etc) will range from large holes to fine.
The only requirement for the size of the holes in your beads is that the holes must be large enough that the string (or wire) that you are using can fit through the holes. Other than that, the holes (or beads) can be any size you like.
You cannot blanket a large sphere wit smaller spheres because spheres cannot tessellate. There are always gaps between adjacent spheres and so no blanketing is possible.
Theoretically they can be as large as a small star or as large as a galaxy
500 Meters aka quite large! half a kilometre
stellar black holes were stars (these are large)primordial black holes were pieces of the big bang (these are microscopic)
craters
colander or strainer