on a sidenote: I'm pondering about that 2mm spacer layer. It could get built in such a way that it closes the basically open and dust-scooping half above the keyboard. This (together with another few small mechanical/ID changes like closing the AV plug aperture) would largely increase the survival chances of a device dropped into water for 0.8s, and should also help when you're at the beach with all that sand.
/j