Well, let me re-phrase that - I have access to a D12, but don't actually have it in my hands. The PDF manuals from Directv's web site don't give any kind of measurements, or for that matter, specifications at all.
The measurements you pulled from Google - were they for the D11-500, or one of the other variants such as the -300?
I saw on solidsignal's website that they list the same size measuremens for the D11-500 and the D12, but I need to be sure. I figured one of the system integrators lurking here would know off the top of their head....
Worse case is I'll grab my tape measure and stop at a CC or Bestbuy and meaure one.