My Planck layout:

Got only four layers, but I wanted the modifiers to be symmetrical. I tried combining more modifiers for more layers, but the super/windows-shortcuts are uncomfortably enough as-is.
I really like the numpad-layout, it’s much easier for me to type numbers without alternating hands.
The copy/paste/undo shortcuts on the left side are an ugly necessity of a different layout, so I can use them while the right hand is on the mouse.