For comparison,
I run a 15* angle on the bottom (not departure angle- just on the bodywork) and have not had any problems, even off-roading.
The rear plate holding the lights and license plate is 36x7". The entire boat tail extends the rear end by 41". I have no problems parking in standard spots or parallel parking, since it's shorter than a new Suburban, with a comparatively shorter wheelbase to boot.
Straight side view before it was painted. The stock bumper ends about where the vertical piece of tape is.
Progresssss by
Tyler Linner, on Flickr
The rear ends up looking like this:
Rear by
Tyler Linner, on Flickr