I forgot to mention in my review that you will need to get some more standoffs if you are to stack these.
You will need some female-male M3 standoffs with a length of around 30mm.
You can also get a M3 threaded rod that you cut and screw in to one end of the original female-female standoffs.
Both these items are quite easy to find and costs a couple of dollars for enough to stack at least three.