Chrysler apparently uses nonstandard blades, at least for their PT Cruiser. I have the same experience with the rear wiper, the specified wiper blade extends beyond the bounds of the window area. I wasn't too worried as it actually clears a bit more of the visible window area. Because of my experience with the rear wiper, I measured the front wiper blades when it came time to replace them. I discovered that each blade was about a half inch shorter than the specified replacement. I guess Chrsyler wants you to purchase an OEM blade.
The only solutioin I could think of would be to drop to the next lower sized blade. I don't remember what size the rear takes, but for example, if it took a 17" blade, you would drop to a 16" blade. This of course would result in a bit of underwipe.
I just did a search on wiper blades for the PT, Drivewire lists the size of the rear blade at 16.7" so it is 3/10" under the specified 17" blade.