Just regular headers are already very long. Male + female = 10.83mm. I can combine this with a board to board spacer of 11.1mm to hold the display firmly in place. The only issue with that is the waste of space.
See the photo below:
With a 6.4mm spacer, the distance looks much nicer, but the display headers do not enter the through board header (from Samtec). Notice that the socket is mounted on top of the board to reduce the space below the board.
To reduce the space I have to either use:
- Longer pins on the display, through board socket op the top, like photo above.
- Shorter pins on the display, low profile socket on the bottom.
- Another option might be a through board header from wurth on the bottom:
This allows the display pins to go through the board a tiny bit, for a total board to board distance of 7.1mm
I almost have 10 boards ready. I don't want to solder many more 0603 resistors by hand 
I would like to make these prototypes available to developers that can write code for it.
Sorry @avidan, I am looking for people that can make stuff, not break stuff now. It is to early for breaking stuff as a lot fo the software still has to be ported.
@BDub, PM me if you want a board.
Others that think they can help significantly with writing the software (LCD/touch screen, OneWire, RS485), send me a PM as well. I will look at your forum activity and code contributions, because my supply is limited.
BTW, already found one design flaw: I need pull down resistors on the 125D inputs. When the pins are set to input on the spark, just looking at the board can enable the buzzer (floating pins). The spark will set them to output of course, but pull down resistors for when the bootloader is active is wise.