I'm working on the same project and found this thread searching (again) for more info on extusb. The solution I came up with for getting enough clearance to use the port requires disassembly and if you plan on keeping the warranty, it's probably not a good option for you.
Anyway, my solution was to make some small right-angle brackets for the pcb that contains the extusb port. It requires material for the angle brackets and two small screws with nuts. See attached for a better idea.
I actually got the tablet installed and fairly well, but have since removed it to come up with better designs for charging, access to the power button (and possibly volume buttons) for recovery actions, turning the screen on/off with ignition, and potentially microphone relocation.
You may want to check out http://www.dealextreme.com/
for right-angle and other adapters if you don't want to open up the tablet.
PS: Protect that screen. The plastic is very soft and will easily scratch.