That looks quite neat, I'm going to have to do something similar and "factory style" to get the SG2 into George a little better than it is just now...
Original plan was to build it into the centre console at the top but in this version the sat nav lives there under a pop-up cover.
My worry about just mounting it in the middle of the dash is that someone will want to remove it without permission. Where it is just now is slightly hidden behind the A-pillar but it makes it hard to read in sunlight.
The traditional place, on top of the steering column, is out because of the closeness of the speedo to the wheel and I prefer it in the line of sight so low down on the dash or on the rear view doesn't work for me.
I'm going to try and make some kind of mounting for the top of the dash, maybe in the black correx which I have just now. Thing is with George being so new (newer than I expected) everything has to be "factory" or its not going on...