Quoted from Billy16:
Nope, won't work. The backbox won't clear the top of the lift gate opening. You can only get a pin in about 3/4 of the way, the backbox wedges against the gate opening, then you have to tie down the lift gate. How do I know? I did it once, never again.
I'm with you on that one. I have heard from a previous owner that a pin wouldn't fit in a HHR, but as someone else mentioned. A pin will fit fine in a PT Cruiser.