Based on my reading Unity 2D is limiting the maximum acceleration of 2D Gravity using RagidBody2D. As such, it is necessary to alter the tk2dCamera Pixels per Meter. That said, when I changed this setting I had a number of issues / questions... As such, I made a short video with the questions because there were just two many screen shots needed:
1) Why are the movement handles for the tk2dCamera being displayed off to the right, rather than the origin?
2) Why are the movement handles for the screen named "TruckScreen" off the right, but all other screens look correct?
3) When I change the tk2dCamera Pixels per Meter setting to 100, why does the Preview and Game windows look so incorrect?
Here is the video with the questions:
http://www.youtube.com/watch?v=X2dw6S5-QcU&feature=youtu.be