So made some progress this afternoon on the install.
Got the Nexus mounted up on the fascia kit. I used a hard back cover, some L brackets and 2 part epoxy. 2 holes drilled in to each air conditioning ducts saw it held quite well just using small screws and bolts.
I then worked on moving the I/O assembly from the base of the Nexus to the back as there is not enough room to connect the OTG cable. This was done by removing the back cover & battery, prying up the copper battery shield and straightening out the ribbon cable across to the opposite side of the tablet. I then cut a hole in the back cover and hard case and mounted the I/O assembly in a junction box which I gutted using a dremel. More 2 part epoxy on the hard case and done!
To tidy things up and take the strain off the connection of the OTG to the USB port I simply used a cable to tie to secure it in place. Will probably use another cable tie to secure the OTG cable to the hard cover as well.