I smell a ticket or two in your future.
Why? Is there some threshhold that makes it illegal to use a 9.5" GPS when a 3" or 4" is ok?
Too bad BT Stack GPS doesn't pick up the iPhone's GPS signal and send it to the iPad.
OP: What GPS receiver are you using? It's nice to know which ones work well.
Here is a simple, cheap way to install the iPad on your dash...
http://www.cultofmac.com/42011/an-ipad-car-mount-for-peanuts-plus-an-apple-ipad-case/