This is a fantastic matrix-testing toy!
If you're working with 4 layers, I think this pattern works great:
(image having difficulty being viewed, so i'll transcribe it below)
1 0 0 0 0 0 0
0 0 1 0 0 0 0
0 0 0 0 0 1 0
0 1 0 0 0 0 0
0 0 0 0 0 0 0
1 0 0 0 1 0 0
0 0 0 0 0 0 1