Too much is just enough.
Hmmm. Why not just design the system to work like the Panamera's? Design the transfer case to work off of the TKO or other Tremec, maybe use adapter plates for various transmission choices. This way, you have almost equal length drive shafts. The only issue would be that the rear diff would be slightly off center. This keeps it all in one nice little area, and allows you to bias the power sent to the front / rear quite easily, in the center of the whole vehicle. Something to think about.