Picked up an HHR back in 2008 because it was the smallest car that could carry my largest plane. Actually it can carry two or three most of the time. There are trap doors at the rear to access tail lamps from inside. I picked up a spare pair at the local junkyard and used them to mount the Powerpole outlets. The HHR battery is at the rear below a trap door makes wiring a breeze. While I was at it I added a cigarettte lighter outlet as well.