I've done as you suggest Steve - double sided taped the cradle to the wall of the battery well, then run an RJ45 extension along the tunnel, connecting up to the handpiece which is double sided taped to the dash. Aerial coax also runs along the tunnel, up the driver footwell, and through the firewall to the top right of the accelerator, which was an absolute bastard of a job that was.
Haven't noticed any interference from the battery, and the wiring was super easy given its proximity. The bonus is I can have the UHF running without the vehicle on. The downside is I have to remember to turn it off! This Uniden unit has a low voltage cutout though, which makes things easier.
Edit: had some rotation issues with the images - for clarity, the unit is mounted on the transmission tunnel side of the battery.
