May I make a suggestion, WFD? I would love it if you could place the standoffs in the exact positions they are in the stock Poker case. That is, four standoffs, designed to be in the same positions as the two leftmost standoffs and two rightmost standoffs in the Poker case. Theoretically, one could then take a saw to a plastic Poker case, cut out the middle portion, and epoxy the left and right bits together to form a plastic case for the GHpad. That also gives you the location of the USB connector.
Edit: I'm also hoping this design principle will serve as a guide to komar007 when designing the PCB for the GHpad.
Edit 2: Where are my manners? That case is freaking AWESOME! Thanks, WFD!